3 


A  LABORATORY  GUIDE 

FOR 

GENERAL  BOTANY 

GAGER 


FROM  THE  LIBRARY  OF 
WILLIAM  A.  SETCHELL,i864-i943 

PROFESSOR  OF  BOTANY 


MOf  QT.Y  r  1RRARV 


WltUAM  4.  SE7CH£LLt 
Vf  CXUF&IWIA, 


A  LABORATORY  GUIDE 

FOR 

GENERAL  BOTANY 


G  A  GER 


BY  THE  SAME  AUTHOR 


FUNDAMENTALS 

OF 

BOTANY 

1 2 mo,  xix  +  640  Pages,  435  Illustrations.     Flexible 
Cloth,  Round  Corners,  $1.50  Postpaid. 

P.  BLAKISTON'S  SON  &  CO.,  PHILADELPHIA 


A  LABORATORY  GUIDE 

FOR 

GENERAL  BOTANY 


BY 

C.  STUART  GAGER 

DIRECTOR  OF  THE  BROOKLYN  BOTANIC  GARDEN 


PHILADELPHIA 

P.  BLAKISTON'S  SON  &  CO. 

1012  WALNUT  STREET 
1916 


COPYRIGHT,  1916,  BY  P.  BLAKISTON'S  SON  &  Co. 


THE  MAPLE   PRESS   YORK.  PA 


PREFACE 

This  LABORATORY  GUIDE  is  intended  for  the  use  of 
students  in  their  first  course  in  universities  and  colleges, 
or  other  institutions  doing  work  of  similar  grade.  It  is 
not  a  teacher's  manual,  and  therefore  does  not  include 
information  as  to  laboratory  equipment,  the  purchase  and 
care  of  apparatus  and  materials,  nor  references  to  the 
literature.  The  author  believes  that  botanical  instruc- 
tion in  America  has  now  reached  a  stage  where  such 
directions  to  university  instructors  is  no  longer  necessary 
nor  appropriate. 

As  to  the  most  desirable  kind  of  laboratory  directions 
there  is  a  wide  diversity  of  opinion  among  teachers  of  ex- 
perience. This  GUIDE  has  been  prepared  in  harmony 
with  the  theory  that  the  beginning  student  needs  to  learn, 
in  his  first  laboratory  course,  not  merely  botanical  facts, 
but  how  to  observe  and  how  to  record  his  observations. 
It  is  believed  that  rather  full  directions,  such  as  are  given 
in  the  following  pages,  will  accomplish  this  result.  In 
advanced  courses  the  student  should,  of  course,  be  ex- 
pected to  work  with  increasing  independence,  both  in 
his  thinking  and  his  handling  of  apparatus  and  material. 
The  GUIDE,  substantially  as  here  offered,  has  been  used 
with  a  number  of  large  beginning  classes. 

The  order  of  topics  follows  that  in  the  author's  Funda- 
mentals of  Botany,  but  with  only  minor  changes  the 
GUIDE  may  be  adapted  for  use  with  any  text.  - 

The  author  is  indebted  to  Dr.  E.  W.  Olive  for  his  care- 
ful reading  of  portions  of  the  page  proof. 

C.  STUART  GAGER. 

BROOKLYN  BOTANIC  GARDEN, 
October  14,  1916 

v 

M246583' 


CONTENTS 

PAGE 

To  the  Student I 

PART  I 

ANATOMY    AND    PHYSIOLOGY 

Meaning  of  the  Terms .    .    . ,......*-..  9 

A  Generalized  Plant  (Spirogyra) n 

A  Specialized  Plant  (e.g.,  The  Bean  Seedling)  .    ......    \    .  16 

Structure  of  the  Foliage  Leaf  .   .............    \    .  17 

Transpiration »    • 22 

Absorption  of  Water  by  Plants  .    ........;.....  29 

The  Path  of  Water  in  the  Plant.   .    .    .    ..   :   .    .    .  '.  (.-  .    .    ,    .  34 

Mechanical  Uses  of  Water  in  the  Plant    ...,...".....  36 

Nutrition    .-   .    .  .... •  . »  ".'  . 39 

The  Occurrence  of  Carbohydrates  in  Plants 40 

Formation  of  Carbohydrates  ,    .    .    ...    .    .    .    ,    .    .    .-  ...  45 

Alcoholic  Fermentation 5° 

Respiration -.,...;....  53 

The  Influence  of  External  Conditions  on  the  Plant 56 

PART  II 

MORPHOLOGY   AND   LIFE    HISTORY 

Meaning  of  the  Terms •    •    •  59 

An  Outline  of  the  Classification  of  Plants 61 

Directions  for  Study 63 

Polypodium  vulgare  (Common  polypody) 63 

Polytrichum  commune  (Common  hair-cap  moss)   ....,».  74 

Marchantia  polymorpha  (A  liverwort) 84 

Fucus  vesiculosus  (Bladder  wrack)    .    .  ,.    .    .    .    ...    .    .  96 

Vaucheria  sessilis  (Green  felt) .    .    .  102 

Spirogyra  (Pond  scum,  Green  silk). 106 

Pleurococcus  vulgaris  (Green  slime) '•   .•    •    •    •  IIQ 

Phycomyces  nitens  (or  Rhizopus  nigricans) 113 

Saprolegnia  (Water  mold) 117 

Albugo  Candida  (Blister  blight) 121 

Agaricus  campestris  (Meadow  mushroom) 125 

vii 


V1J1  CONTENTS 

PAGE 

Puccinia  graminis  (Wheat  rust) I3o 

Isoetes  (Quillwort) I34 

Equisetum  (Horsetail) I4o 

Lycopodium  (Club-moss) I44 

Selaginella  (Little  club-moss) I47 

Zamia  floridana  (A  cycad) !53 

Pinus  laricio  (Austrian  pine) ^i 

Trillium  (Wake-robin) I 


A  LABORATORY  GUIDE  FOR 
GENERAL  BOTANY 


TO  THE  STUDENT 

THE    NATURE   AND   PURPOSE    OF   LABORATORY  WORK 

A .  The  Laboratory: 

1.  The  word  laboratory  is  derived  from  the  Latin  word 
labor,  meaning  work.     A  laboratory,  therefore,  is  a 
workshop.     The  essential  part  of  laboratory  work, 
however,  is  not  the  manual  but  the  intellectual. 
Handling  specimens,  manipulating  apparatus,  tak- 
ing notes,  and  making  drawings,  all  are  essential, 
but  are  wholly  secondary  to  thinking.     A  laboratory 
exercise  should  be  regarded  always  and  primarily  as 
a  thought  exercise.     Everything  else  that  you  do 
with  a  specimen  should  be  secondary  to  thinking 
about  it,  and  done  only  to  aid  thought. 

2.  The  aim  of  laboratory  work  is  to  obtain  facts  at  first 
hand.     Reading  books  on  plants  is  only  studying 
about  botany.     To  study  botany  one  must  have  the 
actual  plants  before  him.     It  was  Louis  Agassiz 
who  said,  "  If  you  study  nature  in  books  when  you 
go  out  of  doors  you  cannot  find  her."    The  posses- 
sion of  this  first-hand  knowledge  makes  the  reading 
of  botanical  books  not  only  more  easy,  but  vastly 
more  interesting.     You  can  take  more  away  from 
the  text  because  you  bring  more  to  it. 


GUIDE   FOR   GENERAL  BOTANY 


3.  Another  aim  of  laboratory  work,  not  less  important 
than  the  one  just  mentioned,  is  to  acquire  scientific 
habits  of  thought  and  work;  to  learn  the  method  by 
which  knowledge  of  the  given  science  is  acquired. 
The  scientific  method  differs  from  the  unscientific 
in  laying  emphasis  upon  the  absolute  necessity  of 
an  orderly  procedure  in  thinking  and  doing,  upon 
willingness  to  put  aside  prejudice  and  preconceived 
notions,    upon   scrupulous   neatness,    accuracy   of 
thought  and  work,  and  careful  attention  to  minute 
details.     The  scientific  method  is  not  peculiar  to 
the  natural  sciences:  it  is  just  as  essential  in  history 
or  language-study  as  elsewhere,  and  the  highest 
success  in  any  intellectual  pursuit  is  not  possible 
if  the  requirements  of  the  scientific  method  are  dis- 
regarded. 

B.  Observation: 

4.  Observation  is  not  merely  looking  at  a  thing.     It 
means  looking  for  a  purpose.     The  mental  attitude 
of  the  true  observer  is  that  of  a  questioner.     The 
great  Swiss  botanist,  de  Candolle,  said,  "The  in- 
terrogation point  is  the  key  to  all  the  sciences." 
Observation,  then,  consists  in  asking  as  definite 
questions  as  possible  about  natural  objects,  and 
seeking  their  answer,  not  from  the  instructor  or 
the  text-book,  but  from  the  object  itself. 

5.  Remember  that  your  specimen  is  the  final  authority 
in  all  matters  of  fact.     Your  first  question  should 
never  be,  "What  ought  I  to  see?"     "How  many 
parts  ought  the  specimen  to  have?"  but  always, 
without  exception,  "What  do  I  see?"     "How  many 
parts   does   the   specimen  have?"     Possibly   your 
specimen  may  be  found  to  differ  from  that  of  your 
neighbor,  or  from  the  descriptions  in  the  books. 


TO   THE    STUDENT  3 

If  so,  record  that  fact,  and  endeavor  to  ascertain 
whether  your  specimen  is  abnormal,  or  whether 
your  observation  of  it  is  at  fault  in  any  way. 
Always  try  to  see  all  you  can  with  the  unaided  eye 
before  resorting  to  the  aid  of  a  hand  lens  or  microscope. 
C.  Experimentation: 

6.  In  mere  observation  one  takes  conditions  as  he  finds 
them;  in  experimentation,  he  determines,  within 
limits,  the  conditions  under  which  the  observation 
is  made.     It  is  never  possible  to  control,  absolutely, 
all  the  conditions  in  any  experiment,  but  this  is 
partly  compensated  for  by  arranging  side  by  side  of 
the  experiment  proper,  a  check  or  control.     In  the 
experiment  and  control  all  conditions  should  be  as 
nearly  alike  as  possible  save  one.     The  golden  rule 
in  experimenting  is:  vary  only  one  condition  at  a 
time.     Then  if  the  experiment  and  control  give 
unlike  results,  we  are  justified  in  attributing  the 
difference  to  the  unlike  factor. 

7.  Before  beginning  an  experiment,  the  object,  or  aim, 
of  the  experiment  must  be  clearly  conceived  and 
clearly  stated.     The  necessary  materials  and   ap- 
paratus should  next  be  decided  upon  and  procured. 
Then  may  follow  the  operation,  that  is,  the  arrange- 
ment of  the  materials  and  apparatus  in  a  suitable 
way.     This  step  is  frequently  referred  to  as  "set- 
ting up"  the  experiment.     The  record  of  it  should 
include  an  accurate  statement  of  the  conditions  at 
the   beginning  of   the  experiment,   together  with 
drawings   of   the   apparatus   and  material  as  the 
experiment  is  set  up. 

Next  follows  the  observation,  which  must  always  be 
made  and  recorded  at  the  time  and  place  of  the  experi- 
ment. It  should  include  suitable  drawings.  Fin- 


4  A  LABORATORY  GUIDE  FOR  GENERAL  BOTANY 

ally,  there  may  be  stated  the  inference,  that  is,  the 
conclusion  or  conclusions  which  are  thought  to  be 
justified  by  the  facts  observed. 

The  record  of  an  experiment,  then,  should  follow 
the  outline  given  below: 

1.  Object. 

2.  Materials   and   apparatus    (with   drawings). 

3.  Operation. 

4.  Observation  (with  drawings). 

5.  Inference. 

6.  Remarks. 
D.  The  Note-book: 

8.  The  Note-book  serves  two  purposes:    First,  the 
making  of  it  gives  you   opportunity  to   acquire 
facility  in  describing  what  you  observe.    This  is 
not  an  easy  accomplishment,  but  a  very  essential 
one.     "The  greatest  thing  a  human  being  ever  does 
in  this  world"  said  John  Ruskin,  "is  to  see  something, 
and  tell  what  he  saw  in  a  plain  way" 

9.  Secondly,  the  note-book  serves  as  an  index,  to  the 
instructor,  of  what  you  have  done  and  how  well 
you  have  done  it.     In  addition  to  these  two  pur- 
poses, the  note-book  will  be  a  permanent  record 
for  your  own  future  use.     It  should   contain  a 
complete  record  of  all  you  observe,  and  the  infer- 
ences you  make  from  these  observations.     It  should 
include    written    descriptions    and    drawings.     In 
both  the  latter  the  aim  should  be  accuracy,  neatness, 
completeness,    conciseness.    Above   all   things,   it 
should  be  a  record  of  your  own  observation,  not 
of  your  neighbor's.    If,  as  may  happen  on  rare 
occasions,  it  becomes  necessary  to  use  your  neigh- 
bor's notes,  always  state  the  fact  clearly  and  frankly 
in  your  own  book. 


TO   THE    STUDENT  5 

10.  In  writing  your  notes,  the  aim  should  be  to  give 
such  a  clear  account  of  what  you  have  seen  and  done 
that  anyone  else  who  knew  nothing  of  the  subject 
could  profit  by  reading  them.    In  other  words, 
aim  to  make  your  notes  usable  in  the  future.    Your 
text-book  may  be  regarded  in  one  sense,  as  the 
author's    laboratory    note-book.     Seek    to    make 
your  laboratory  note-book  an  accurate  and  readable 
illustrated  text  on  the   ground   covered  by  your 
course. 

E.  Laboratory  Drawings: 

11.  Drawing  is  one  of  the  greatest  aids  to  observation. 
This  is  its  main  purpose  in  the  laboratory.     It 
is  often  said  that  "persons  who  cannot  draw  cannot 
see."    This   is   probably   an   extreme    statement, 
but  it  is  undoubtedly  true  that  one  who  can  make 
an  accurate  drawing  of  a  thing  has  observed  it 
more  accurately  than  one  who  cannot. 

12.  Laboratory  drawings  should  aim  to  represent  the 
thing  only  as  it  is,  not  as  it  may  impress  one  at 
first  sight.    They  differ  in  this  respect  from  the 
work  of  the  artist.     For   example,   to   show   the 
exact  number  and  location  of  the  veins  of  a  leaf 
would  ruin  the  artist's  picture;  but  without  those 
details  the  laboratory  drawing  would  be  of  little 
value. 

13.  As  directed  in  the  GUIDE,  make  as  thorough  an 
observation  of  the  object  as  possible  before  you 
begin  to  draw;  then  make  the  drawing. 

14.  Unless  otherwise  directed,  make'  outline  drawings, 
shading    only    where    absolutely    necessary.     In 
general,  every  line  in  your  drawing  should  represent 
some  fact  of  structure  in  the  specimen. 

15.  Be  sure  to  make  the  drawing  large  enough  so  that 


A  LABORATORY  GUIDE  FOR  GENERAL  BOTANY 

all  details  may  be  included  without  crowding  or 
confusion. 

1 6.  First  sketch  in  the  outline  lightly  with  a  5H  drawing 
pencil.     In  finishing  a  2H  pencil  may  sometimes  be 
desirable. 

17.  All  drawings  should  be  on  unruled  sheets,  and  only 
on  one  side  of  the  sheet.     They  should  be  labeled 
and  numbered  consecutively  throughout  the  course 
by    writing    under    each    the    abbreviation    Fig., 
followed  by  the  proper  numerals,  and  then  by  the 
legend  or  label,  stating  what  the  object  is,  and  what 
view  of  it  is  shown,  as  for  example,  " Cross-section, 
end  view."     Each  drawing  should  have  all  of  its 
essential    parts     labeled     by    extending    straight 
horizontal    dotted   lines    from    the   various   parts 
(using  a  ruler),  and  writing  the  name  of  the  part 
at  the  end  of  the  line. , 

1 8.  The   arrangement  of   the   drawings   on   the  page 
should  receive  careful  attention,  so  as  to  make  as 
attractive  and  well  balanced  a  page  as  possible. 
Crowding  should  be  avoided,  and  on  any  one  page 
should  be  included  only  those  drawings  that  repre- 
sent parts  of  the  same  plant,  or  pertain  to  the 
same  subject. 

19.  The  various  pages  of  drawings  should  be  numbered 
and  labeled  near  the  top  of  the  page  at  the  middle 
thus;  Plate  I.     Throughout   your   written   notes, 
when  describing  a  structure  or  apparatus,  repre- 
sented by  a  drawing,  refer  to  the  drawing  by  its 
proper  number  and  the  number  of  the  Plate  (e.g., 
Plate  IV,  Fig.  5). 

20.  At  the  completion  of  the  course,  arrange  a  "Table 
of  Contents,"  listing  the  main  topics,  as  indicated 
in  the  LABORATORY  OUTLINE,  in  the  order  in  which 


TO    THE    STUDENT  7 

they  occur  in  the  note-book,  with  the  page  number 
near  the  right-hand  edge,  and  a  neat  dotted  line 
extending  from  the  subject  to  the  page  number. 
F.  The  Microscope: 

21.  Full  directions  for  the  use  and  care  of  the  compound 
microscope  will  be  giver/  by  the  instructor.  The 
student  should  clearly  realize  from  the  first  that  the 
science  does  not  reside  in  the  instrument.  The  latter 
is  merely  an  aid  to  the  eyes,  but  not  to  the  mind, 
and  is  made  necessary  by  the  limited  range  of  our 
unaided  vision.  It  should  be  used  only  after  one  has 
seen  all  that  he  possibly  can  with  the  unaided  eye. 

22..  The  following  points  should  be  constantly  borne 
in  mind : 

(a)  Keep  all  parts   of   the  instrument,   especially 

the  lenses,  scrupulously  clean. 

(b)  Never  attempt  to  take  the  instrument  apart. 

(c)  Never  remove  lenses  from   the   stand.     If  it 
is  ever  absolutely  necessary  to  do  so,  then 

(d)  Never  lay  a  lens  down  on  the  table. 

(e)  Never  touch  the  lens  with  the  fingers  or  eyelids. 
(/)  Never  try  to  clean  the  lens  with  the  handkerchief 

or  anything  except  lens  paper, 
(g)  Never   examine  any  object  without  covering 

it  with  a  cover-glass. 

(ti)  Never  allow  the  objective  to  touch  the  cover- 
glass. 
(i)    Never  focus    down    while    looking    through    the 

microscope, 
(k)  Be  sure  that  the  slides  and  covers  are  absolutely 

clean.     Dirt  will  be  magnified  as  well  as  the 

object  you  are  studying. 
(0    Handle  all  slides  and  cover-glasses  by  the  edge, 

never  touching  their  surface  with  the  fingers. 


A  LABORATORY  GUIDE  FOR  GENERAL  BOTANY 

(m)  Don't  shut  one  eye  when  looking  through 
the  instrument.  Ability  to  work  with  both 
eyes  open  is  easily  acquired,  is  much  less 
tiring,  and  is  an  advantage  in  many  ways. 

(n)  Never  use  high  powers  when  low  powers  will  serve. 

(o)  Examine  all  objects  with  the  low  power  first, 
then  with  the  high  power,  if  necessary. 

(p)  Never  set  the  instrument  away  with  a  micro- 
scopic slide  under  the  objective,  nor  with  the 
high-power  objective  over  the  aperture. 

(q)  When  the  laboratory  period  is  over,  remove 
the  preparation  you  have  been  studying,  and 
leave  the  microscope  with  the  low-power 
objective  over  the  aperture. 


PART  I 
ANATOMY  AND  PHYSIOLOGY 


I.  MEANING  OF  THE  TERMS 

A.  Plant  physiology  is  that  branch  of  botany  which  deals 
with  the  vital  activities  of  plants.    But  physiological 
processes  or  functions  are  carried  on  by  various  parts 
of  the  plant,  and  these  parts  all  have  their  own  char- 
acteristic structure.    In  order  to  understand  the  proc- 
esses we  must  know   the  internal   as   well   as   the 
external  structure  of  the  parts  concerned.     This  knowl- 
edge requires  dissection,  and  this  phase  of  the  science 
is,  therefore,  called  anatomy.     Microscopic  anatomy  is 
called  histology.     Just  as  the  processes  cannot  be 
intelligently   considered   apart  from    the    structures 
involved,  so,  also,  the  study  of  anatomy  apart  from 
physiology  is  meaningless. 

B.  In  the  lowest  (i.e.,  most  simply  organized)  plants  all 
functions,  both  nutritive  and  reproductive,  are  per- 
formed by  every  structural  unit  or  cell;  but  in  more 
highly  organized  plants  there  are  special  parts  or 
organs  for  the  performance  of  each  function;  for  ex- 
ample, roots  to  take  in  moisture,  flowers  to  form  seed. 
In  other  words,  in  the  higher  plants  there  is  a  division 
of  physiological  labor,  or,  as  it  is  sometimes  called,  a 
physiological  division  of  labor.    While  not  entirely 
wanting,  the  division  of  physiological  labor  is  less 
marked  in  the  lowest  plants. 

9 


10  ANATOMY  AND   PHYSIOLOGY 

Because  they  are  composed  of  organs,  plants  and 
animals  are  termed  organisms. 

C.  Thus  we  see  that  some  plants  have  a  generalized  plant- 
body,  others  a  more  highly  specialized  one.  To  under- 
stand the  various  life-processes  carried  on  by  plants, 
we  must  have  a  knowledge  of  their  structure.  A  gen- 
eralized plant  will  be  studied  first,  then  the  structure 
of  a  higher  (i.e.,  more  highly  specialized)  plant.  This 
will  be  followed  by  an  elementary  study  of  the  funda- 
mental life-processes  involved  in  the  nutrition  and 
growth  of  the  individual.  The  second  part  of  the 
course  will  be  devoted  to  studying  the  various  kinds 
of  plants,  and  the  numerous  ways  in  which  different 
kinds  of  plants  solve  these  same  life-problems  of  nutri- 
tion and  reproduction. 


II.  A  GENERALIZED  PLANT  (Spirogyra) 

A.  Naked-eye  Characters: 

1.  Carefully  take  a  small  bit  of  this  plant  between  the 
thumb  and  fingers  and  note  its  "feel."     Suggest 
why  it  is  sometimes  referred  to  as  "green  silk." 

2.  Carefully  lift  up  some  of  the  material  with  a  needle, 
and  describe  the  form  of  the  plant.     How  many 
centimeters  long  are  the  longest  filaments  you  can 

%        observe? 

3.  Can  you  detect  any  evidences  of  a  differentiation 
of  the  plant  into  shoot  (i.e.,  stem  and  leaves)  and 
root  ? 

B.  Microscopic  Characters: 
i.  The  plant  as  a  whole. 

(a)  Mount  two  or  three  filaments  in  water. 

(b)  Note  that  the  filament  is  composed  of  separate 
structural   units,   placed   end   to   end.     These 
units  are  cells. 

(c)  Are  the  filaments  more  than  one  cell  thick? 
Do  they  branch?     Are  they  of  uniform  diame- 
ter?    Compare  the  length  of  the  various  cells 
with  each  other.     Compare  the  shape  of  the 
end  cell  with  that  of  the  others.     What  is  the 
shape  of  the  filament  as  seen  in  imaginary  cross- 
section?     Very  careful  focussing  is  necessary  in 
order  to  answer  this  question  correctly. 

(d)  Accurately  measure  the  length  (in  millimeters) 
of  a  piece  of  filament  lying  straight  under  the 
cover-glass,  then  count  the  number  of  cells  in 

ii 


12  ANATOMY  AND  PHYSIOLOGY 

this  piece.  Calculate  the  average  length  of  the 
cells,  and  the  number  of  cells  in  the  longest 
filament  observed.  Estimate  the  length  of  an 
individual  cell  in  terms  of  its  diameter,  and  from 
this  calculate  the  diameter  of  the  filament. 

(e)  Using  the  low  power  and  removing  the  cover- 
glass,  carefully  cut  a  filament  apart  with  the 
scalpel,  causing  as  little  injury  as  possible.  As 
you  do  this  observe  the  exposed  end-walls  of 
the  uninjured  cells  that  now  terminate  the  fila- 
ment where  it  was  broken  apart.  Describe  and 
try  to  account  for  what  you  see.  Is  there  any 
evidence  of  the  existence  of  a  force  within  the 
cell?  If  so,  in  what  direction  does  it  act? 
Make  two  outline  drawings,  showing  the  con- 
ditions before  and  after  cutting. 

(/)   Make  a  diagram  about  75  mm.  long,  illustrating 
the  outline  of  the  three  terminal  cells  of  a  fila- 
ment, as  seen  in  optical  section.     Omit  all  de- 
tails of  cell-structure. 
2.  The  individual  cell. 

(a)  Center  your  attention  on  any  one  of  these  cells, 
and  identify  the  following  organs  of  the  cell : 

(1)  A  cell-wall,  enclosing  all  other  parts  of  the 
cell.    Is  it  transparent  or  not?     Give  a 
reason  for  your  answer.    Note  its  relative 
thickness.    The  wall  is  composed  of  cellu- 
lose.    Has  each  cell  its  own  end -wall,  or  is 
there  a  common  end-wall  for  two  adjacent 
cells? 

(2)  The  substance  enclosed  by  the  cell-wall  is 
largely  living  matter,  or  matter  in  the  living 
state.    It  is  called  protoplasm.    The  unit 
of  protoplasm  of  each  individual  cell  is 


A   GENERALIZED   PLANT  13 

called  a  protoplast.    Distinguish  the  follow- 
ing parts  of  a  protoplast: 

(3)  The  prominent  green  chlorophyll-band,  or 
chromatophore.    Describe    its    form,    the 
number  of  turns  it  makes  in  the  cell,  and 
the  outline  of  its  margin.    Infer  its  shape 
in  cross-section.     How  many  in  each  cell? 
If  more  than  one,  do  they  coil  in  the  same 
direction?     Can  you  detect  free  ends  of  the 
chromatophore?    Are  they  continuous  from 
cell  to  cell?     The  color  of  the  chlorophyll- 
band  is  due  to  the  presence  of  a  green  pig- 
ment, chlorophyll. 

(4)  The  denser  areas  within  the  chromatophore 
are   regions   of   starch-formation.     In   the 
center  of  this  area  is  the  starch-forming 
body,  or  pyrenoid.     Surrounding  the  pyre- 
noid  are  starch  grains. 

(5)  Make  a  detailed  drawing,  10  mm.  wide  and 
15  mm.  long,  showing  the  details  of  struc- 
ture of  a  portion  of  the  chlorophyll-band, 
as  seen  under  high  power.     Indicate  on  the 
drawing  the  names  of  all  parts  shown. 

(6)  At  or  near  the  center  of  the  cell  find  a  dense, 
colorless  body,  the  nucleus,  surrounded  by 
a  less  dense  layer  of  colorless  cytoplasm. 
Describe  the  shape  of  the  nucleus.     From 
the  layer  of  cytoplasm  trace 

(7)  Delicate  cytoplasmic  strands,  extending  to 
the  pyrenoids,  and  to 

(8)  The  lining  layer  of  cytoplasm.    This  layer 
(sometimes  called  "  primordial  utricle  ")  is 
in  intimate  contact  with  the  entire  inner 
surface  of  the  cell-wall,  and  is  difficult  to 


14  ANATOMY  AND   PHYSIOLOGY 

identify.     Its    two    surfaces    are    plasma 
membranes. 

(9)  The  clear  spaces  in  the  cell  are  vacuoles, 
filled  with  cell-sap. 

(10)  Make  a  drawing  of  a  cell  at  least  10  cm.  in 
longest  measure. 

( 1 1)  The  lining  layer  may  be  easily  demonstrated 
as  follows:   Place  a  drop  of  a  5  per  cent, 
solution  of  common  salt  (sodium  chloride) 
at  one  edge  of  the  cover-glass.     Be  careful 
that  none  of  the  solution  runs  over  onto  the 
cover-glass.     By  placing  a  small  piece  •  of 
blotting  paper  at  the  opposite  edge  of  the 
cover-glass,  the  water  will  be  removed,  and 
the  salt  solution  drawn  under  the  cover- 
glass,  irrigating  the  specimen.     Follow  with 
another    drop    if    necessary.     Observation 
should  be  continuous  while  the  specimen 
is  being  irrigated  with  the  solution. 

(12)  Describe  the  effect  of  the  salt  solution  on 
the  lining  layer. 

(13)  Loosening   the  lining  layer,   as  above,   is 
|        termed  plasmolysis  (i.e. ,  loosening  the  plasm) . 

The  cell  is  said  to  be  plasmoly zed. 

(14)  Make  a  drawing,  the  same  size  as  the  pre- 
ceding, showing  a  plasmolyzed  cell. 

(15)  Before  plasmolysis  the  lining  layer  was  held 
close   against   the   cell-wall  with  a   force, 
already  detected   (e,  p.    12),   sufficient  to 
cause  a  rigid  condition  of  the  cell  called 
turgor  or  turgidity. 

(16)  Now  replace  the  salt  solution  with  fresh 
tap-water,  by  the  method  described  in  (n) 
above.     Describe   the   effect   on   the   cell. 
What  condition  has  been  restored? 


A   GENERALIZED   PLANT  1$ 

3.  Make  a  diagram,  at  least  25  mm.  in  diameter,  show- 
ing the  appearance  of  a  cell  in  imaginary  cross- 
section  taken  through  the  nucleus. 

4.  Do  you  think  Spirogyra  is  a  unicellular  or  a  multi- 
cellular  plant?     If  the  latter,  how  many  cells  con- 
stitute one  plant?     Give  reasons  for  your  opinion 
either  way. 

NOTE.— If  time  permits,  the  study  of  cell-structure  may  be  ex- 
tended by  observing  the  cells  in  young  leaves  of  Elodea,  the  skin 
(epidermis)  of  onion  scales,  the  basal  cell  of  the  hairs  on  any  seed- 
ling cucurbit,  or  the  cells  of  the  stamen  hairs  of  Tradescantia. 


III.  A  SPECIALIZED  PLANT  (e.g.,  The  Bean  Seedling)1 

A .  The  plant  as  a  whole: 

1.  Examine  the  seedling  given  you  and  note  that  it  is 
composed  of  an  aids  with  appendages;  the  axis,  of 
root  and  shoot;  the  root,  of  a  primary  root  with 
branches  (secondary  roots);  and  the  shoot,  of  a 
main  stem,  bearing  leaves.    Has  the  main  stem 
branches?    Is  this  true  of  all  plants?    What  is  the 
difference  between  a  stem  and  a  branch? 

2.  Describe  fully  the  location  of  the  leaves  and  their 
attitude  on  the  stem.    Do  they  occur  on  both  the 

^main  stem  and  its  branches?  The  places  on  the 
fstem  where  leaves  grow  are  nodes.  The  spaces 
between  the  nodes  (vertically)  are  called  internodes. 

3.  Compare  the  size  of  the  upper  with  that  of  the  lower 
Bangle  made  by  the  leaves  with  the  stem.    This 
Jupper  angle  is  called  the  leaf-axil  (Latin  axilla, 
^armpit). 

4.  Do  you  find  any  structures  in  the  leaf-axils?    If  so, 
^describe  them.     What  are  they? 

5.  With  what  do  the  tips  of  the  main  stem  and  branches 
terminate? 

6.  Describe  any  other  outgrowths  of  stem  or  branches. 

7.  Make  a  drawing  of  the  plant  as  large  as  your  draw- 
ing paper  will  permit,  showing  all  parts  referred  to 
above. 

1  This  study  may  or  may  not  be  omitted,  depending  upon  the  previous 
preparation  of  the  students,  and  the  time  available. 


16 


IV.  STRUCTURE  OF  THE  FOLIAGE-LEAP  (e.g.,  Lilac 

Leaf) 

.  External  Characters: 

1.  Make  a  drawing,  natural  size,  showing  all  the  parts 
of  the  foliage-leaf  given  you,  as  seen  from  the  under 
side. 

2.  Identify  the  following  parts,  and  label  them  suit- 
ably on  your  drawing: 

(a)  The  flat,  expanded  blade.    Describe  its  colora- 
tion (i.e.y  the  kind  and  distribution  of  color). 
Is  the  blade  simple  (i.e.,  not  divided  into  leaf- 
lets), or  compound  (i.e.,  branched,  divided  into 
leaflets)?    The  surface  that  lies  uppermost,  as 
the  leaf  bends  back  from  its  position  in  the  bud, 
is  the  ventral  surface;  the  under  surface  is  the 
dorsal  one.     These  terms  are  applied  with  ref- 
erence to  the  position  of  the  leaf  in  the  bud. 

(b)  The  leaf-apex,  which  is  also  the  apex  of  the 
blade. 

(c)  The  margin  of  the  blade. 

(d)  The  base  of  the  blade. 

(e)  The  venation  (distribution  of  veins  in  the  blade) . 
Describe  it  as  parallel-veined,  pinnately  netted- 
veined  (with  a  midrib),  or  palmately  netted- 
veined.     Describe  the  difference  between  the 
three  types  of  venation.    Is  there  a  marginal 
vein?    If  so,  suggest  what  advantage  it  may 
be  to  the  leaf. 

(/)  The  petiole  (stem  of  the  leaf).    Leaves  having 

a  petiole  are  petiolate,  otherwise  sessile. 
2  17 


1 8  ANATOMY  AND   PHYSIOLOGY 

(g)  The  leaf -base,  the  portion  by  which  the  leaf  is 
attached  to  the  branch. 

(h)  If  present,  the  stipules,  outgrowths  of  the  leaf- 
base.  Leaves  without  stipules  are  exstipulate. 

(i)  Before  the  next  class  exercise  compare  with  the 
leaf  studied,  as  directed  above,  various  other 
types  of  leaves  collected  by  yourself,  making 
full  drawings  and  notes. 

B.  Anatomy  of  the  Leaf: 

THE   LOWER   EPIDERMIS1 

1.  As  directed  by  the  instructor,  remove  a  strip  of 
the  lower  epidermis  of  a  foliage-leaf,  and  mount 
it  in  water  or  clearing  fluid,  being  sure  to  have  the 
outer   surface   uppermost.     Record   the   name   of 
the  species. 

2.  Note  the  cellular  structure  of  the  epidermis.    A 
group  of  cells,  similar  in  structure  and  function, 
is  called  a  tissue.    The  leaf-epidermis  is  epidermal 
tissue.     The  cell-wall  forms  a  box,  having  depth  as 
well  as  length  and  breadth.     Note  that  you  see 
only  the  edges  of  the  vertical  walls.      How  many 
are  there?    Are  there  other  walls?    If  so,   how 
many?    Are  they  visible?    Explain.     Make  a  dia- 
gram of  an  epidermal  cell  as  seen  in  perspective. 
Are  the  cell- walls  transparent  or  opaque?     Give 
a  reason  for  your  answer.     Suggest  the  advantage 
of  this  feature  to  the  plant. 

3.  Observe    the    somewhat    lenticular    openings,    or 
pores,  each  surrounded  by  crescent-shaped  cells. 

1Miss  ECKERSON  (Bot.  Gaz.,  46:  221-224.  81908)  has  recommended 
the  leaves  of  the  following  plants  as  specially  satisfactory  for  the  study 
of  the  epidermis  and  stomata:  Sunflower,  Fuchsia  speciosa,  zonal  Gera- 
mium,  and  Tradescantia  zebrina. 


STRUCTURE    OF   THE   FOLIAGE-LEAF  1 9 

The  openings  are  stomata  (Latin  singular,  stoma,  a 
mouth).  The  crescent-shaped  cells  are  guard-cells. 
How  many  has  each  stoma? 

4.  Do  the  guard-cells  and  other  epidermal  cells  contain 
chlorophyll-bodies   (chloroplasts)  ?    Describe  their 
shape.     They  are  not  considered  identical  with  the 
chlorophyll-band  of  Spirogyra,  hence  the  different 
name. 

5.  Note   the   shape  and   arrangement  of   the   other 
epidermal  cells.     Are  they  in  the  same  plane  as 
the    guard-cells?    Describe,    giving    reasons    for 
your  answer. 

6.  State  the  number  of  stomata  visible  in  the  entire 
field    (high   power).     Record    three    counts,    each 
of  a  different  area,  and  the  average.     Why  is  this 
desirable?    After  ascertaining  the  area  of  the  ob- 
jective of  your  microscope,  calculate,  from  several 
counts,  the  average  number  of  stomata  per  square 
centimeter. 

7.  Make  a  drawing  showing  at  least  three  stomata 
with  their  guard-cells  and  adjacent  epidermal  cells. 
The  guard-cells  should  be  at  least  15  mm.  long. 

THE   UPPER    EPIDERMIS 

8.  As  directed  in  B,  1-6  above,  study  the  structure 
of  the  upper  epidermis  of  the  same  leaf.     Draw. 

9.  Compare  the  structure  of  the  upper  with  that  of 
the  lower  epidermis,  noting,  among  other  features, 
the  relative  number  of  stomata  in  each. 

10.  In  the  light  of  the  experiments  on  transpiration,1 
what  do  you  think  is  one  function  of  these  stomata? 
Of  the  guard-cells? 

1  This  takes  for  granted  that  class  demonstrations  of  transpiration  have 
been  given. 


20  ANATOMY  AND  PHYSIOLOGY 

11.  Give  one  explanation  of  the  difference  in  the  rate 
of  transpiration  from  the  two  surfaces  of  the  leaf. 
Is  this  the  only  explanation? 

CROSS-SECTIONAL  VIEW 

12.  Mount  free-hand  sections  of  a  fresh  leaf  showing 
the  internal    anatomy  as    seen  in    cross-section. 

13.  Identify  in  your  section  the  two  epidermal  layers. 
How  many  cells  thick  are  they?     Do  you  find 
any  chloroplasts  in  these  layers? 

14.  Are  all  the  epidermal  cell- walls  of  the  same  thick- 
ness?    Describe  any  variations  observed. 

15.  Is  there  a  thick,  continuous  pellicle  over  the  surface 
of  the  leaf?    Is  it  composed  of  cells?     Such  a 
pellicle,  when  it  occurs,  is  called  cuticle. 

1 6.  Compare  the  thickness  of  the  cell- walls  in  the  upper 
and  the  lower  epidermis. 

17.  Note  the  stomata  and  guard-cells,  and  their  relation 
to  the  other  epidermal  cells. 

1 8.  The  tissue  between  the  two  epidermal  layers  is 
composed  chiefly  of  leaf -parenchyma,  or  mesophyll, 
in  which  are  imbedded  the  veins.     Mesophyll,  and 
all  other  tissue  containing  chlorophyll,  whether 
found  in  leaves  or  in  other  organs,  is  also  called 
chlorenchyma.     Note  that  the  mesophyll  is  com- 
posed of  two  distinct  groups  of  cells,  as  follows : 

19.  The  more  compactly  lying  cells  beneath  the  upper 
epidermis  compose  the  palisade  layer,  or  palisade 
parenchyma.    Describe  their  shape,  contents,  rela- 
tive size,  and  relation  to  each  other  and  to  the 
epidermis. 

20.  Between  this  layer  and  the  lower  epidermis  lies  the 
spongy  parenchyma.    Describe  its  appearance,  and 


STRUCTURE    OF   THE   FOLIAGE-LEAF  21 

the  cells  that  compose  it.     Compare  it  with  the 
palisade  layer. 

21.  What  fills  the  space  between  the  mesophyll-cells? 
Do   these  spaces   connect  with  the  outside  air? 
If  so,  how? 

THE  VEINS 

22.  At  certain  regions  the  section  passes  through  veins, 
presenting    either    cross,    longitudinal,    or    other 
sections  of  them.     Note  the  greater  differentiation 
of  the  cells  in  the  veins.     This  differentiation  marks 
the    distinction    between    fundamental    tissue    or 
parenchyma,  and  transformed  tissue,  prosenchyma. 
There  are  several  different  kinds  of  prosenchyma. 

23.  Using  prepared  slides,  supplied  by  the  instructor, 
make  a  drawing  of  the  cross-section  of  a  leaf,  show- 
ing all  features  noted  above.     Make  the  drawing 
at  least  75  mm.  long,  and  be  careful  to  preserve  the 
natural  proportions. 

24.  The  experiments  on  transpiration  have  shown  that 
living  plants  are  constantly  losing  water.    What 
would  be  the  result  if  no  more  were  supplied? 
What  problem  of  plant  life,  therefore,  naturally 
arises? 


V.    TRANSPIRATION1 

A .  Loss  of  Weight  of  a  Growing  plant: 

Experiment  i. — Object:2  To  show  that  a  living  plant 
is  constantly  losing  weight. 

i.  Choose  a  well- watered,  vigorous,  potted  plant. 
Wrap  the  pot  in  sheet  rubber  or  oilcloth  (or  paraf- 
fined paper),  and  tie  the  wrapping  about  the  stem 
tightly,  but  not  tightly  enough  to  cause  injury. 
Place  the  plant  thus  prepared  on  a  pair  of  balances 
in  a  well-lighted  window,  and  record  its  exact 
weight  in  grams  in  the  following  table,  which  should 


Time 

Weight  in 
grams 

Day 

Hour 

be  copied  into  your  note-book.  After  weighing, 
the  window  should  be  opened  (if  the  weather  is  not 
too  cold) ;  direct  sunlight  is  also  desirable.  Record 

1  NOTE. — Where  the  class  is  large,  or  the  laboratory  equipment  limited, 
and  especially  when  the  course  extends  over  only  one  semester,  it  is  rec- 
ommended that  most,  if  not  all,  of  the  physiological  experiments  outlined 
in  the  remainder  of  Part  I  be  performed  by  the  instructor  as  demonstra- 
tions in  the  presence  of  the  class. 

2  For  directions  for  recording  an  experiment  see  p.  4  of  this  GUIDE. 
In  each  experiment  this  outline  is  to  be  filled  out  entire,  without  further 
directions. 

23 


TRANSPIRATION  23 

the  weight  at  five  or  six  successive  periods,  and  then, 
as  directed  by  the  instructor,  plot  on  section-paper 
a  curve  of  your  readings.  Lay  off  the  observed 
weights  as  ordinates,  the  time-intervals  as  abscis- 
sae. Be  sure  that  in  this  and  all  subsequent  ex- 
periments your  inferences  are  only  those  warranted 
by  your  observations. 

Experiment  2. — To  ascertain  one  cause  of  loss  of  weight 
of  plants. 

1.  Take  four  clean,  dry  glass  beakers  or  tumblers,  two 
pieces  of  cardboard  large  enough  amply  to  cover  the 
opening  of  the  beaker,  and  a  vigorous  green  leaf 
having  a  leaf-stalk  and  a  perfectly  dry  surface. 

2.  Fill  two  of  the  glass  beakers  or  tumblers  three- 
fourths  full  of  water,  insert  the  leaf-stalk  through 
a  small  hole  in  the  center  of  one  piece  of  cardboard, 
make  the  opening  as  tight  as  possible  about  the 
leaf-stem,  using  cotton  if  necessary,  and  place  the 
cardboard  over  one  of  the  water-containing  beak* 
ers,  so  that  the  leaf-stalk  extends  down  into  the 
water.    Invert  one  of  the  dry  beakers  over  the  leaf. 
Arrange  the  other  two  beakers  and  cardboard  in 
the  same  way,  only  omitting  the  leaf  and  the  hole 
through  the  cardboard.     This  second  set  of  beak- 
ers is  the  control  (cf.  p.  3,  If 6). 

3.  Place  both  sets  of  beakers  in  a  well-lighted  window, 
preferably  in  direct  sunlight,  and  from  time  to  time 
observe  and  compare  the  appearance  of  the  inner 
surfaces  of  the  inverted  beakers. 

4.  Do  you  notice  any  difference  in  the  result  on  oppo- 
site sides  of  the  leaf?    If  so,  describe. 

5.  Can  you  see  any  water  passing  from  the  leaves? 
In  what  state,  therefore,  does  it  pass  off?    From 
what  part  of  the  leaf  does  it  come?    Why  do  you 


ANATOMY  AND  PHYSIOLOGY 


think  so?  What  change  does  it  undergo  in  order 
to  become  visible  on  the  surface  of  the  beaker? 
In  what  state  does  it  probably  exist  in  the  leaf? 
State  one  reason  why  the  plant  lost  weight  in 
Experiment  i.  Was  this  the  only  cause  of  its  loss 
of  weight? 

6.  The  above  experiments  demonstrate  the  fact  of 

transpiration.     Give  a  definition  of  transpiration. 
B.  The  Control  of  Transpiration: 

Experiment  3. — To  see  if  the  epidermis  affects  the  rate 
of  transpiration. 

i.  Take  two  sound  apples.  Remove  the  skin  (epider- 
mis) from  one  of  them,  then  ascertain  accurately 
and  record  the  weight  of  each,  in  tabular  form,  as 
follows : 


Time 

Weight  in  grams 

Day 

Hour 

Unpared 

Pared 

2.  Place  the  specimens  in  a  convenient  place,  with  free 
access  of  air,  and  out  of  reach  of  mice.   ;  ;. 

3.  Record,  in  a  table  like  the  above,  three  (or  more) 
subsequent  observations  of  weight  at  successive 
class  periods. 

4.  Plot  two  curves  showing  the  rate  of  loss  of  weight. 
Include  these  curves  and  their  interpretation  as 
part  of  your  record  of  the  experiment. 

Experiment- 4.— To   demonstrate   the   effect   of   the 
"skin  "  6!  a  potato-tuber  on  transpiration. 


TRANSPIRATION  2$ 

1.  Proceed  as  directed  for  Experiment  3,  using  two 
sound  potatoes  instead  of  apples. 

2.  The  "skin"  of  an  apple  is  a  true  epidermis,  having 
an  outer  layer  of  cuticle,  which  is  not  readily  per- 
meable by  water.    The  "skin"  of  a  potato- tuber 
is  more  complex,  consisting  of  several  layers,  one 
of  which  is  a  layer  of  cork-tissue.     It  is  this  corky 
layer  which  chiefly  retards  the  loss  or  water  from 
the  tubers. 

Experiment  5. — After  noting  the  color  change  caused 
by  wetting  dry  cobalt  paper  (prepared  by  dipping 
filter  paper  into  a  solution  of  cobalt  chloride  and 
thoroughly  drying  it),  make  the  following  experi- 
ment: Place  discs  of  the  cobalt  paper  (e.g.,  as 
large  as  a  five  cent  piece)  on  opposite  sides  of  a 
lilac  leaf,  and  hold  all  in  place  between  two  micro- 
scopic slides  (or  larger  pieces  of  glass),  fastened 
with  rubber  bands  around  each  end.  Compare  the 
rate  of  color  change  of  the  two  opposite  discs,  and 
infer  the  cause. 

Other  leaves,  having  structural  peculiarities 
similar  to  those  of  the  lilac,  may  be  used;  e.g., 
hibiscus,  osage  orange,  oleander,  lizard's  tail 
(Saururus). 

Experiment  6. — Examine,  with  the  microscope,  strips 
of  both  upper  and  lower  epidermis  of  the  leaf  used 
in  Experiment  5,  and  infer  the  probable  cause  of 
the  differential  color-change  observed. 

Experiment  7. — Place  any  suitable,  well- watered  potted 
plant  on  postal  scales,  "household"  scales,  or  other 
convenient  weighing  device,  after  first  carefully 
wrapping  the  pot  in  sheet-rubber,  or  sheet-oil- 
cloth, as  in  Experiment  i.  Record  the  loss  of  weight 
at  fifteen-minute  (or  other  suitable)  intervals  while 


26  ANATOMY  AND  PHYSIOLOGY 

the  experiment  is  standing  for  an  hour,  each,  in  (a) 
direct  sunlight  and  breeze;  (b)  diffuse  sunlight,  and 
the  comparatively  still  air  of  a  room;  (c)  under  a 
glass  bell-jar,  or  large  box.  The  breeze  may  be 
secured  by  placing  the  experiment  in  or  near  an 
open  window  or  other  draught,  or  by  means  of  an 
electric  fan. 

On  the  basis  of  your  observations  in  Experiment  7, 
discuss  the  control  of  transpiration  by  external 
conditions,  and  suggest  differences  in  the  condition 
of  the  plant  caused  by  its  exposure  in  the  various 
situations  suggested  above,  and  the  effect  this  would 
have  on  the  rate  of  transpiration.  Were  the  results 
observed  in  the  three  situations  strictly  comparable? 
Why? 
C.  One  Effect  of  Transpiration: 

Experiment  8. — To  show  the  so-called  "lifting  power" 
of  transpiration. 

1.  Insert  a  leafy  stem  of  a  living  plant  (a  branch  of  any 
evergreen  is  excellent  to  use)  into  one  end  of  a  piece 
of  glass  tubing  about  3  ft.  long,  of  small  bore,  and 
full  of  tap-water,  taking  special  care  to  have  the 
joint  between  the  stem  and  the  glass  air-tight, 
using  rubber   tubing   for   this   purpose   if   neces- 
sary.    The  experiment  will  be  more  satisfactory 
if   the  stem  is  cut  off  under  water,  and  the  cut 
end  kept  from  contact  with  air,  throughout  the 
experiment. 

2.  After  being  sure  that  the  glass  tube  is  full  of  water, 
place  it  upright  in  a  dish  of  mercury,  having  care 
not  to  allow  any  of  the  water  to  run  out  in  so  doing. 

3.  Place  the  experiment  in  sunlight,  if  possible,  but 
do  not  leave  it  in  direct  sunlight  for  more  than  one- 
half  to  three-quarters  of  an  hour. 


TRANSPIRATION  27 

4.  At  the  beginning  of  the  experiment,  and  at  suitable 
intervals  thereafter,  as  directed  by  the  instructor, 
measure  and  record  the  height  of  the  mercury  in 
the  glass  tube. 

5.  Make  two  drawings  of  this  apparatus  in  longitudi- 
nal section:  (a)  as  soon  as  the  experiment  is  set  up; 
(b)  at  the  close  of  your  final  observation.    Label 
all  essential  parts. 

6.  You  have  made  this  last  experiment  with  a  living 
plant.     The  question  now  naturally  arises:  Is  the 
result  observed  due  to  the  life-factor  involved,  or 
is  it  merely  the  result  of  some  physical  condition, 
as,  e.g.,  the  evaporation  involved?     The  question 
may  be  easily  answered  by  setting  up  an  experiment 
similar   to    the    preceding,    but    using    non-living 
material,  as  follows: 

Experiment  9. — To  see  if  evaporation  exerts  a  "lifting 
power." 

1 .  Tie  a  piece  of  porous  animal  membrane  (e.g.,  bladder) 
over  a  this  tie- tube,  being  sure  that  there  is  no 
chance   for   a   leak   between    the   glass   and    the 
membrane. 

2.  Fill  the  this  tie- tube  with  water. 

3.  Prepare  a  dish  of  mercury  and  also  a  clamp  to  hold 
the  tube  in  place. 

4.  Invert  the  this  tie- tube  and  place  the  lower  end  in 
the  mercury,  being  sure  that  no  air  enters  the  tube. 
By  this  arrangement  all  factors  of  Experiment  8 
have  been  eliminated  except  evaporation,  and  the 
evaporation  takes  place  through  only  one  mem- 
brane, and  that  a  non-living  one.     In  other  words, 
we  have  Experiment  8  reduced  to  its  lowest  terms. 

5.  Observe  and  record  the  height  of  the  mercury  in  the 
tube  as  in  Experiment  8. 


28  ANATOMY  AND   PHYSIOLOGY 

6.  Make  a  drawing  of  this  apparatus  in  longitudinal 
section  at  the  beginning  and  at  the  close  of  the 
experiment,  labeling  all  essential  parts. 

7.  The  conclusions  drawn  from  this  experiment  should 
cover  an  explanation  of  the  bearing  of  these  results 
on  Experiment  8. 


VI.  ABSORPTION  OF  WATER  BY  PLANTS 

A.  External  Anatomy  of  the  Root: 

1.  Examine  roots  of  seedlings  (mustard,  flax,  oats, 
etc.),  grown  in  a  moist  chamber  (e.g,  flower-pot, 
or  saucer  of  same),  and  kept  covered  with  a  glass 
plate  so  as  to  expose  them  to  the  air  as  little  as 
possible.     Note  the  delicate  white  hairs  on  them. 
Describe  their  distribution  and  relative  size.    These 
hairs  are  root-hairs. 

2.  Hold  the  root  up  to  the  light  and  note  the  more 
transparent  tissue  on  the  end  (root-cap),  covering 
the  root-tip   proper.     How  is   the   latter   distin- 
guished?   Is  "root-tip"  synonymous  with  "end  of 
the  root?"     Explain. 

3.  Make  a  drawing  of  the  seedling,  at  least  twice 
natural  size,  showing  these  features.     (The  labeling 
of  the  root-cap  and  root- tip  may  be  deferred  until 
observation  B,  3,  below,  has  been  made.) 

B.  Microscopic  Characters  of  the  Root: 

1.  With  the  scalpel  carefully  remove  the  terminal 
5  to  6  mm.  of  a  root,  with  the  root-hairs,  and  mount 
it  in  water.    Locate  the  oldest  and  youngest  root- 
hairs.     How    are    they    distinguished?     Do    they 
branch?     What  relation  do  the  hairs  bear  to  the  epi- 
dermis?   Are  they  divided  by  cross- walls?    Do  they 
contain  nuclei?    What  is  a  root-hair,  structurally? 

2.  Make  a  drawing  (high  power)  of  three  or  four  hairs, 
showing  their  structure  and  relation  to  the  epider- 
mis.    The  hairs  should  be  drawn  at  least  50  to  75 
mm.  long. 

29 


30  ANATOMY  AND   PHYSIOLOGY 

3.  Distinguish  the  root- tip  from  the  root-cap.  Of 
what  is  the  latter  composed?  Describe  it.  Draw. 

C.  The  Function  of  Root-hairs: 

1.  Carefully  pull  up  a  mustard  seedling  growing  in 
sand  and  having  several  leaves.     Without  injuring 
the  plant,  carefully  and  very  gently  shake  off  all 
sand  that  readily  falls  away.     Does  the  sand  adhere 
with  equal  firmness  to  all  portions  of  the  root? 
Describe  in  detail,   explain,   and  illustrate   by  a 
drawing,  X2. 

2.  Pull  up  another  seedling  of  the  same  age,  and  remove 
all  or  most  of  the  adhering  sand.     Replant  both 
seedlings  in  sand,  water  them,  and  set  them  aside 
until  the  next  period.     In  order  to  eliminate  indi- 
vidual  differences   it   is    necessary    to    treat  several 
seedlings  in  each  of  the  ways  above  indicated. 

3.  At  the  next  meeting  of  the  class  observe  and  com- 
pare  the  appearance  of   the  seedlings.     In   thor- 
oughly removing  the  sand  from  the  seedlings,  how 
were  the  root-hairs  affected? 

4.  By  means  of  what  organs  does  a  land  plant  obtain 
most  of  its  water?     State,   in  a  paragraph,   the 
reasons  for  your  answer. 

5.  We  have  ascertained   the   organs  whose  function 
it  is  to  take  in  water  from  the  soil.     It  is  now 
important   to   inquire   by  what   process  the  soil- 
water  passes  into   the  plant  through  the  organs 
of  absorption. 

D.  How  the  Root-hairs  Take  in  Water;  Osmosis: 

i.  The  preceding  studies  of  the  plant  cell  lead  us  to 
recognize  the  fact  that  the  root-hair  is  an  individual, 
elongated  cell.  Within  is  the  cell-sap,  a  solution 
of  various  salts ;  without,  as  the  plant  grows  in  the 
soil,  is  the  soil- water,  also  containing  numerous  sub- 


ABSORPTION  OF  WATER  BY  PLANTS  31 

stances  in  solution.     The  cell-sap  of  the  root-hairs, 
and  the  soil  water,  are  solutions  of  different  densi- 
ties, and  separated  by  layers  of  porous  (semiper- 
meable)    plant    substance.     Name    these   layers. 
Experiment  10. — To  see  what  results  when  two  liquids 
of  unequal  density  are  separated  by  a  porous  mem- 
brane: 

2.  With  a  pen  knife  or  a  pair  of  scissors,  remove  a 
portion  of  the  shell  from  the  large  end  of  a  hen's 
egg,  taking  great  care  not  to  puncture  the  mem- 
brane that  separates  the  white  of  the  egg  from  the 
shell. 

3.  Carefully  place  the  egg  thus  prepared  upright  in 
a  glass  tumbler,  or  beaker,  and  pour  in  tap-water 
until  the  water  surface  is  about  i  in.  above  the 

egg- 

4.  By  the  above  arrangement  the  solution  of  various 
salts  intermingled  with  the  substance  of  the  egg 
serves  as  the  more  dense  liquid,  the  water  outside 
as  the  less  dense,  while  the  membrane  in  the  egg 
acts  as  the  porous  membrane,  separating  the  two 
liquids.     In  other  words,  we  have  roughly  imitated 
the  plant  cell,  though  there  is  nothing  in  the  cell 
that  corresponds  to  the  shell  of  the  egg. 

5.  Make  a  careful  drawing,  showing  the  experiment 
in  longitudinal  section,  and  about  one-half  natural 
size.    Label  all  parts. 

6.  Make  an  observation  at  the  end  of  an  hour;  of 
two  hours.     Describe  what  results,  and  illustrate 
the    final    result    by    another    sectional    drawing 
opposite  the  first  one. 

7.  State  as  clearly  as  you  can  what  has  taken  place 
in   order   to   produce   the   result   observed.     The 
process  is  termed  osmosis  (Greek,  osmos,  pushing). 


32  ANATOMY   AND   PHYSIOLOGY 

8.  In   this  experiment,   what  part  of   the  root-hair 
does  the  egg  membrane  represent?  the  solution  of 
salts  in  the  egg?  the  water  in  the  beaker? 

9.  From  the  above  study  explain  what  takes  place 
when  a  root-hair  is  in  moist  soil.     What  is  thus 
accomplished  for  the  plant? 

10.  Define  osmosis. 

Experiment  n. — To  demonstrate  osmosis  in  a  plant 
cell: 

11.  Mount    in    water    several    uninjured    root-hairs. 
Again  identify   (high  power)    the  lining  layer  of 
cytoplasm.     Make  a  drawing  of  one  of  the  root- 
hairs  about  50  mm.  long.    Leave  room  for  two 
other  drawings  by  the  side  of  the  first  one.     Run 
a  drop  of  a  5  per  cent,  salt  solution  under  the 
cover-glass.     This  solution  is  more  dense  than  the 
cell-sap. 

12.  Describe  the  effect  of  the  salt  solution  on  the  proto- 
plast. 

13.  Make  a  drawing  by  the  side  of  the  first  one,  showing 
what  you  observe.    What  is  the  process  called? 

14.  Now  thoroughly  irrigate  the  cells  with  fresh  water, 
and  observe  and  describe  the  result.     Explain  as 
fully  as  you  can. 

15.  By  the  side  of  your  second  drawing  make  a  third, 
showing  the  cell  as  it  appears  after  irrigation  with 
fresh  water. 

1 6.  In  a  sentence,  name,  in  order,  two  processes  that 
take  place,  (a)  when  a  living  plant  cell  is  immersed 
in  a  solution  more  dense  than  the  cell-sap;  (b)  when 
a  plasmolyzed  cell  is  irrigated  with  tap-water. 

17.  What  is  one  function  of  the  salts  dissolved  in  cell- 
sap?    What  is  one  function  of  the  plasma  mem- 
brane? 


ABSORPTION  OF  WATER  BY  PLANTS  33 

Experiment   12. — Demonstration  of   the  Osmoscope 
(by  the  instructor).* 

1 8.  Make  a  drawing  showing  clearly  all  essential  parts 
as  seen  in  longitudinal  section,  and  describe  the 
apparatus  as  set  up  and  explained  by  the  instructor. 

19.  Record  observations  on  the  height  of  the  column 
of  water  in  the  tube  of  the  osmoscope: 

(a)  At  the  beginning  of  the  experiment. 

(b)  On  successive  half-hours. 

(c)  On  successive  days. 

20.  Explain  the  results  observed. 

Experiment  13. — Demonstration   of  "  exudation-pres- 
sure" (by  the  instructor). 

21.  Describe  and  make  a  drawing  of  the  experiment  at 
its  beginning,  as  set  up  by  the  instructor. 

22.  Complete  your  observations  and  record  as  directed 
under  Experiment  12,  naming  the  species  of  plant 
used. 

23.  Compare  the  conditions  and  results  in  this  experi- 
ment with  those  in  Experiment  12. 

*It  is  here  taken  for  granted  that  the  instructor  will  be  able  to 
make  this  demonstration  (as  well  as  that  under  Experiment  13)  without 
further  suggestions,  using  any  one  of  the  various  types  of  osmoscope 
commonly  found  in  botanical  laboratories. 


VII.  THE  PATH  OF  WATER  IN  THE  PLANT 

Experiment  14. — To  see  if  there  are  definite  channels 
for  the  passage  of  liquids  through  a  stem. 

1.  Place  the  cut  ends  of  various  living,  leafy  shoots 
(e.g.,  corn,  plantain,  lily  leaves,  parsnip,  or  seed- 
lings of  castor-oil  plants),  into  a  solution  of  fuchsin 
or  of  eosin,  and,  after  they  have  stood  for  a  suitable 
time,   as   determined  by   the   instructor,   observe 
freshly  exposed  end-surfaces,  and  note  the  regions 
where  the  colored  solution  appears.     Does  it  pass 
up  through  the  whole  mass  of  tissue,  or  are  there  def- 
inite channels  through  which  it  rises?     Cut  sections 
of  the  stems  at  various  heights,  and  observe  and 
describe  the  distribution  of  the  colored  areas. 

2.  Compare  the  distribution  of  the  colored  areas  in  a 
parsnip  (or  seedling  of  a  castor-oil  plant)  and  a 
stalk  of  corn  (or  petiole  of  some  lily  leaf).     Make 
a  diagram  to  illustrate  this. 

3.  Examine  the  end  of  a  dry  corn  stalk,  and  note  the 
projecting  strands.     What  relation  do  they  bear  to 
the  paths  of  the  eosin?    They  are  composed  of 
fibers  and  vessels  united,  and  are  therefore  called 
fibro -vascular  bundles. 

4.  Carefully  cut  the  epidermis  in  a  ring  around  the 
petiole  of  a  leaf  of  plantain,  being  specially  careful 
not  to  cut  clear  through  the  petiole. 

5.  Taking  the  end  of  the  petiole  in  one  hand  and  the 
leaf-blade  in  the  other,  gently  pull  the  two  portions 
of  the  petiole  a  short  distance  apart.     Describe  and 

34 


THE  PATH  OF  WATER  IN  THE  PLANT        35 

illustrate  by  a  drawing  what  you  observe.     What 
structures  are  thus  disclosed? 
What  relation  do  the  fibre-vascular  bundles  bear 
to  the  veins  of  the  leaf?     To  the  root-hairs? 
Write  a  clear  statement  of  how  the  water  passes 
from  the  soil  into  the  roots  of  a  plant,  and  into  and 
through  the  leaves  and  out  into  the  air,  mentioning, 
in  order,  all  parts  and  processes  studied. 


VIII.  MECHANICAL  USES  or  WATER  IN  THE  PLANT 

A .  Rigidity  and  Maintenance  of  Form: 

Experiment  15. — To  ascertain  the  cause  of  rigidity  in 
beet  tissue: 

1.  From  a  beet  cut  four  slices  about  5  mm.  thick, 
10  mm.  wide,  and  75  mm.  long. 

2.  Place  the  slices  as  follows: 

(a)  In  tap- water. 

(b)  In  a  10  per  cent,  salt  solution. 

(c)  and  (d)  In  boiling  water  for  two  or  three  min- 
utes. 

Then  place 

(c)  In-tap  water,  and 

(d)  In  the  10  per  cent,  salt  solution. 

3.  At  the  end  of  fifteen  minutes  observe  and  record 
the  relative  rigidity  of  the  various  slices,  ascer- 
tained by  carefully  bending  them. 

4.  Thoroughly  rinse  the  slices,  b   and   d,   and  then 
transfer  them  to   tap-water.    At  the  end  of  an 
hour  (or  sooner)  observe  them  again  and  describe 
the  result. 

5.  Explain  your  observations  on  the  basis  of  your 
previous  experiments. 

6.  What  is  one  mechanical  use  of  water  in  a  plant 
tissue,  and  how  is  this  accomplished? 

Experiment  16. — To  demonstrate  longitudinal  tissue- 
tension. 

7.  Obtain  a  petiole  of  rhubarb,   or  burdock,   or  a 
stalk  of  celery.     With  a  scalpel  make  a  lengthwise 

36 


MECHANICAL  USES   OF   WATER  IN  THE   PLANT  37 

cut  for  a  distance  of  about  25  mm.  from  the  end, 
and  just  beneath  the  surface. 

8.  Describe  the  position  assumed  by  the  severed  piece. 
Illustrate  by  a  diagram,  natural  size. 

9.  From  another  petiole  cut  off  a  portion  at  least 
15  cm.  long,  with  the  cut  surfaces  normal  to  the 
edges.     Record  the  exact  length  of  the  piece  in 
millimeters. 

10.  With  a  scalpel  carefully  remove  a  thin  strip  of 
outer  tissue  along  the  entire  length  of  the  piece 
(or  remove  a  strip  of  "bark"  from  a  very  young 
woody  stem).    At  once  try  to  replace  it.     Has  it 
altered  in  length?    If  so,  describe.     Make  another 
similar  observation  at  the  end  of  ten  or  fifteen 
minutes.    What  would  you  have   to   do   to   the 
strip  to  make  it  resume  its  former  length? 

11.  Carefully  measure  the  length  of  the  excised  strip 
about  fifteen  minutes  after  its  removal.     Record 
this  measure,  and  calculate  the  percentage  of  change 
in  length. 

12.  From  another  portion  of  the  petiole  cut  off  two 
strips  from  opposite  sides   (or  the  bark  from  a 
portion  of  some  young  woody  stem).    Place  one 
of   the   excised   strips  in  water,  another  in  a  10 
per  cent,  salt  solution. 

13.  At  the  end  of  five  or  ten  minutes  compare  the 
lengths  of  the  two  strips,   (a)  with  each  other, 
(b)  with  the  portion  of  the  stem  from  which  they 
were  cut.    Explain  what  you  observe. 

14.  From  the  preceding  studies  describe  the  condition 
of  the  tissues  in  a  plant  stem.    To  what  is  this 
condition  due? 

15.  Of  what  advantage  do  you  think  this  condition 
would  be  to^the  plant? 


38  ANATOMY   AND   PHYSIOLOGY 

Experiment    17. — To   demonstrate   transverse   tissue 
tension. 

16.  Take  short  portions  (about  15  or  20  mm.  long) 
of  some  woody  stem  15  to  20  mm.  in  diameter, 
and  with  the  scalpel  make  a  clean  cut  lengthwise 
through   the  bark,   and   remove   the   bark,   being 
careful  not  to  crack  or  break  it. 

17.  At  once,  or  at  the  end  of  four  or  five  minutes, 
try  to  replace  the  bark.     Describe  your  success 
in  so  doing.     Draw,  end  view  and  side  view. 

1 8.  What  must  be  done  to  the  bark  in  order  to  restore 
its  original  length? 

19.  From  this  study  what  further  do  you  know  of  the 
condition  of  the  tissues  in  a  plant  stem?     Explain. 


IX.  NUTRITION 

A.  The  nutrition  of  plants,  is  very  similar  to  that  of 
animals,    with   the    exception    that   all   green   plants 
manufacture  their  food  out  of  inorganic  chemical  com- 
pounds.   Animals  cannot  do  this.     They  must  conse- 
quently receive  their  food  ready-made.     But  there  are 
some  lower  organisms  (doubtfully  animals)  that  pos- 
sess the  ability  to  elaborate  their  food  out  of  inorganic 
compounds,  while  on  the  other  hand,  certain  plants, 
such,  for  example,  as  the  mushrooms  and  other  plants 
wanting  chlorophyll,  lack  this  power. 

B.  The  manufacture  of  carbohydrates  is,  in  many  respects, 
the  most  important  function  of  green  plants.     With- 
out it  life  would  be  impossible,   so   that  its  study 
becomes  of  very  great  interest.     We  will  first  learn 
how  to  detect  the  presence  of  a  carbohydrate  such  as 
starch,  then  study  its  occurrence  in  plants,  and  finally 
the  process  by  which  it  is  made  out  of  simpler  chemical 
compounds. 


39 


X.  THE  OCCURRENCE  OF  CARBOHYDRATES  IN  PLANTS 

.  The  Test  for  Starch: 

Experiment  18. — To  ascertain  the  test  for  the  presence 
of  starch. 

1.  Place  a  bit  of  corn  starch,  about  the  size  of  a  small 
shot,   into  a   test-tube   one-fourth  full  of  water. 
Shake  it  thoroughly.     Is  starch  soluble  in   cold 
water?     Give  a  reason  for  your  answer? 

2.  Bring  the  starch  mixture  to  a  boil  over  the  flame 
of  an  alcohol  lamp,  or  Bunsen  burner.    Describe 
the  result.    Is  starch  soluble  in  hot  water?     Give 
a  reason  for  your  answer. 

3.  Set  this  test-tube  aside  to  cool  for  a  moment  or 
two. 

4.  Into   a   test-tube   one-fourth  full   of   clear  water 
place  3  or  4  drops  of  iodine  solution,  using  a  pipette. 
Shake  the  mixture  and  describe  the  color. 

5.  Now  place  i  or  2  drops  of  the  iodine  into  the 
cooled,  boiled  starch  mixture.     Shake  the  mixture 
and  describe  the  resulting  color. 

6.  Pour  one-half  of  this  mixture  into  another  test-tube 
one-half  full  of  water.    What  color  appears? 

7.  Describe  a  test  for  the  presence  of  starch.     (NOTE: 
The  iodine  is  not  the  test;  it  is  only  the  reagent 
used.) 

Experiment  19. — To  see  if  there  is  starch  in  (a)  seeds; 
(b)  stems;  (c)  roots. 

40 


OCCURRENCE  OF  CARBOHYDRATES  IN  PLANTS     41 

8.  Boil  in  water,  in  a  test-tube,  portions  of  the  above- 
mentioned  parts  of  plants,  and  proceed  with  the 
starch  test,  as  above  outlined.     Record  the  experi- 
ment as  usual.     Be  careful  to  distinguish  between 
your  observations  and  your  inferences. 

Experiment  20. — Microchemical  tests  for  starch. 

9.  If  time  permits  of  individual  tests  by  the  student, 
microchemical  tests  may  be  made  by  mounting  in 
water,  on    microscopic  slides,  small   portions  of, 
first,  commercial  starch;  second,  material  scraped 
from  any  soaked  seeds  (e.g.,  corn,  bean),  a  potato- 
tuber  (a  stem),  any  convenient  fleshy  root,  in  each 
case  observing  (and  drawing)  the  shape,  surface- 
markings,  and  characteristic  groupings  of  the  starch 
grains,  then  running  under  the  cover-glass  a  drop 
of  iodine  solution,  and  observing  the  color  reaction. 

Experiment  21. — To  see  if  there  is  starch  in  leaves. 

10.  Extract  the  chlorophyll  from  leaves  of  nasturtium, 
bean   seedling,    or   other   convenient  large-leaved 
plant,  by  placing  the  leaf  first  in  hot  water  to  facili- 
tate the  extraction;  second,  in  hot  alcohol,  or,  after 
they  have  been  dipped  in  hot  water,  the  leaves  may 

.be  left  in  cold  80  per  cent,  alcohol  until  the  following 
class  period. 

11.  Describe  the  effect  of  the  alcohol  on  the  color  of  the 
leaf,  and  state  your  inferences  as  to  the  solubility 
of  chlorophyll. 

12.  Place   the  leaf  in  a  watch-glass,  and   irrigate   it 
with  iodine  solution.    After  a  few  moments  pour 
off  the  iodine,  and  observe  the  color  of  the  leaf. 
This  last  observation  is  often  made  more  striking 
by  placing  the  leaf  on  a  small  piece  of  glass,  and 
holding  it  to  the  light.     State  your  inferences  from 
this  observation. 


42  ANATOMY   AND   PHYSIOLOGY 

13.  If  preferred,  de-chlorophyllized  leaves  may  be  cut 
into  small  pieces,  boiled  in  water  in  a  test-tube  over 
a  Bunsen  flame,  and  the  water  then  tested  for  the 
presence  of  starch. 
B.  Test  for  Sugar: 

1.  We  have  seen  that  starch  is  a  practically  insoluble 
carbohydrate.     We  also  know  that  sugar  is  a  read- 
ily soluble  carbohydrate.     The  chemical  formula  for 
a  molecule  of  starch  is  CeHioOs.     If  we  combine 
with  this  molecule  one  molecule  of  water  (H^O)  we 
have  a  molecule  whose  composition  is  represented 
by  the    formula   C6Hi2O6   L(C6Hio05)n  +  H20  = 
CeHijOj.     This  is  grape  sugar.     Sugar,  then,  differs 
from  starch  in  possessing  relatively  more  hydrogen 
and  oxygen  in  its  molecule.     The  process  of  con- 
verting starch  into  sugar  is  termed  hydrolysis,  and 
since  it  converts  an    insoluble    substance  into  a 
solubile  one,  it  is  a  kind  of  digestion. 

2.  The  sugar  ordinarily  used  for  culinary  purposes  is 
cane  sugar.     Its   formula  is   C^H^On.     Explain 
how  cane  sugar  differs  from  starch  chemically. 

Experiment  22. — To  demonstrate  a  test  for  the  presence 
of  grape  sugar  (C6Hi2O6). 

3.  The  reagent  commonly  used  for  this  test  is  called 
Fehling's  solution,  from  the  name  of  the  scientist 
who  first  employed  it.    The  solution  is  prepared 
by  mixing  one  volume  of  each  of  the  following  stock 
solutions  with  two  volumes  of  distilled  water  (e.g., 
10  c.c.  of  each,  and  20  c.c.  of  distilled  water). 

(1)  17.5  grams  of  copper  sulphate  dissolved  in  500  c.c. 
of  distilled  water. 

(2)  86.5  grams  of  sodium-potassium- tartrate  (Ro- 
chelle  salts)  in  500  c.c.  of  distilled  water. 


OCCURRENCE  OF  CARBOHYDRATES  IN  PLANTS     43 

(3)  60  grams  of  sodium  hydrate  in  500  c.c.  of  dis- 
tilled water. 

The  mixture,  properly  made,  has  a  clear  blue 
color. 

If  the  Fehling's  solution  is  not  freshly  prepared, 
it  should  be  tested,  before  using,  by  heating  a  por- 
tion in  a  test-tube  until  it  boils.  If  a  precipitate 
of  red  copper  oxide  does  not  form  the  solution  is 
good.  It  is  better  to  make  this  test  even  with  fresh 
solution. 

4.  Place  a  very  small  amount  of  grape  sugar  into  a  test- 
tube  one-third  full  of  water. 

5.  Shake  the  solution  and  gently  warm  it,  then  add  a 
few  drops  of  Fehling's  solution. 

6.  Describe  what  results.     The  effect  is  due  to  the 
grape  sugar  reducing   (i.e.,   taking  oxygen  from) 
Fehling's  solution,  forming  cuprous  oxide. 

7.  State  the  test  for  grape  sugar. 

Experiment    23. — To    demonstrate    a     test    for     the 
presence  of  cane  sugar. 

8.  Proceed  as  in  the  preceding  experiment,  using  cane 
sugar  instead  of  grape  sugar.     Observe  and  describe 
the  result. 

9.  Prepare  a  second  test-tube  with  a  solution  of  cane 
sugar. 

10.  Add  several  drops  of  hydrochloric  acid,  and  boil  the 
mixture. 

1 1 .  Now  add  several  drops  of  Fehling's  solution  (enough 
to  neutralize  the  acid). 

12.  State  the  test  for  cane  sugar. 

Experiment  24. — To  demonstrate  the  occurrence  of 
sugar  in  plant  tissues. 

13.  Test  portions  of  onion,   beet,   sweet  corn,   sweet 


44  ANATOMY  AND  PHYSIOLOGY 

potato,  etc.,  for  sugar.    Describe  the  result  in  each 
case. 

14.  Write  a  brief  summary  of  what  you  have  learned 
concerning  the  occurrence  and  distribution  of  carbo- 
hydrates in  plants. 


XI.  FORMATION  OF  CARBOHYDRATES 

A .  The  Conditions  Necessary  for  Carbohydrate  Formation: 
Experiment  25. — To  ascertain  if  light  is  necessary  for 

carbohydrate  formation. 

1.  A  green  leaf,  previously  partly  shaded  by  having  a 
strip  of  black  cloth  closely  affixed  to  both  sides,  is 
to  be  tested  for  starch  as  described  under  Experi- 
ment 21,  after  having  been  in  the  sunlight  for  several 
hours.     Record  as  previously  directed.* 

Experiment  26. — Is  chlorophyll  necessary  for  carbo- 
hydrate formation? 

2.  As  directed  under  Experiment  21,  test  a  variegated 
leaf,   having  white   areas   devoid   of   chlorophyll. 
Make  three  drawings  of  the  leaf,  as  follows:  (a) 
showing  (by  shading)   the  distribution  of  chloro- 
phyll in  the  tissues;  (b)  showing  the  leaf  decolorized; 
(c)  showing  (by  shading)  the  areas  that  gave  the 
starch  reaction  with  iodine. 

B.  E/ects  of  Light  on  Chlorophyll: 

Experiment  27. — To  show  the  need  of  sunlight  for  the 
formation  of  chlorophyll  by  chloroplasts. 

1.  Examine  a  seedling  of  any  convenient  plant  that 
has  been  allowed  to  develop  in  darkness.     Compare 
its  color  with  that  of  another  seedling  of  the  same 
species  grown  in  daylight. 

2.  Now   place   the   seedling  in   diffuse   sunlight   for 
twenty-four  to  forty-eight  hours.     Record  the  re- 
sult, and  state  your  inferences. 

*The  "light  screen,"  devised  by  Professor  Ganong,  for  experiments  in 
starch  formation  by  leaves,  is  specially  recommended  for  this  experiment. 

45 


46  ANATOMY  AND  PHYSIOLOGY 

C.  The  Exchange  of  Gases  in  Photosynthesis: 

Experiment  28. — To  demonstrate  the  evolution  of  gas 
in  photosynthesis. 

1.  Observe  uninjured  branches  of  Elodea  growing  in 
water  in  direct  sunlight.     (For  individual  experi- 
ments one  or  two  branches  in  a  large  test-tube  of 
tap- water  will  serve.)     Describe  what  you  observe, 
coming  from  the  basal  ends,  or  other  parts  of  the 
stems. 

2.  Shade  the  plants  for  a  moment  by  interposing  a 
note-book  or  other  convenient  screen  between  them 
and  the  sun.     Describe  how  the  process  just  ob- 
served is  affected. 

3.  Make  a  diagram  of  the  apparatus  and  material, 
showing  what  you  have  observed. 

4.  Observe  the  bubbles  among  a  mass  of  any  green 
alga  floating  in  water,  and  explain  their  presence. 

Experiment  29. — To  demonstrate  what  gas  is  given  off 
in  photosynthesis. 

5.  With  a  rubber  band,  or  other  convenient  means, 
fasten  together  (not  too  tightly)  the  cut  ends  of  10 
or  15  clean  branches  of  Elodea,  and  place  them  into 
a  glass  funnel,  with  the  cut  ends  extending  upward. 
Invert  the  funnel  into  a  jar  of  water.     The  surface 
of  the  water  should  rise  an  inch  or  two  above  the 
neck  of  the  funnel. 

6.  Fill  a  test-tube  with  water  and  invert  it  over  the 
neck  of  the  funnel,  being  careful  that  no  air  enters 
the  tube. 

7.  Place  the  apparatus  in  bright  sunlight,  and  when 
sufficient  gas  has  been  collected  in  the  test-tube, 
test  it  with  a  glowing  splinter.     How  is  the  splinter 
affected  by  the  gas?     What  gas  does  this  test  indi- 
cate?    The  best  success  of  this  experiment  requires 


FORMATION   OF   CARBOHYDRATES  47 

that  the  gas  be  tested  the  same  day  that  the  experi- 
ment is  set  up.  Especially  avoid  setting  up  the  ex- 
periment in  the  afternoon  and  testing  the  gas  on  the 
following  morning.  Why? 

Experiment  30. — To  demonstrate  what  gas  is  taken 
into  the  plant  in  photosynthesis. 

8.  Into  each  of  three  large  glass  evaporating  dishes, 
A,  B,  and  C,  place  a  glass  bell- jar  having  a  wide, 
open  tubulature  at  the  top.     Into  two  of  the  bell- 
jars,  A  and  B,  place  vigorous,  green-leaved  shoots. 
Into  C  place  no  shoot.     Under  each  bell-jar  place 
a  piece  of  lighted  candle,  2-3  in.  high,  supported 
on  a  flat  cork.     Now  pour  water  into  the  evap- 
orating dishes  until  it  rises  2  or  3  in.  up  the  side 
of  the  bell-jars.     The  burning  of  the  candles  shows 
that  there  is  enough  oxygen  in  the  jars  to  support 
combustion. 

9.  Now  cork  the  bell- jars  air-tight  with  rubber  stop- 
pers.    What  soon  results  to   the  candle  flames? 
What  does  this  tell  you  of  the  amount  of  oxygen 
now  in  the  jars? 

10.  Cover  the  jar  B}  containing  a  shoot,  with  opaque, 
black  cloth,  and  set  all  three  preparations  in  sun- 
light. 

11.  State,  in  a  well- worded  paragraph,  the  condition  in 
each  bell-jar  as  to  light,  chlorophyll,  and  the  com- 
position of  the  air. 

12.  At  the  end  of  two  or  three  hours,  carefully  lower 
into  each  jar,  successively,  a  lighted  candle  attached 
to  the  end  of  a  long  wire.     Record  your  observation 
and  inference  for  each  jar,  and  your  final  inference 
as  to  what  gas  is  taken  into  the  plant  in  photosyn- 
thesis, and  what  conditions  are  necessary  to  the 
process. 


XII.  THE  DIGESTION  OF  STARCH:  TRANSLOCATION 


A.  The  Starch-content  of  Leaves  During  the  Day  and  at 
Night:1 

Experiment  31. — To  find  out  if  starch  is  present  in 
leaves  gathered  in  darkness  as  well  as  in  light. 

1.  Dechlorophyllized  leaves  of  clover  (or  of  one  of  the 
first  five  plants  listed  in  the  table  in  the  foot-note 
below),  collected  (a)  in  bright  sunlight,  (b)  several 
hours  after  sunset,  will  be  tested  by  the  instructor 
for  the  presence  of  starch. . 

2.  Did  both  leaves  probably  contain  starch  during 
the   day?    From   this   experiment   what   do   you 
know  has  taken  place  in  the  leaf  gathered  at  night? 
Is  starch  soluble?    What,  then,  must  have  occurred 
to  the  starch? 

1Miss  ECKERSON  (Bot.  Gaz.,  48:  224-228.  81909)  recommends  the 
following  plants  for  this  study,  since  in  them  photosynthesis  is  very  ac- 
tive, starch  disappears  from  their  leaves  in  darkness  with  comparative 
rapidity,  chlorophyll  is  easily  extracted,  and  the  iodine  reacts  quickly: 


Name    of    Plant 

Disappearance 
of  starch  in 
darkness 
(T.  i8°-22°C.) 

Formation  of  starch  in 
light  (T.  20°-2S°C.) 

Iodine 
test 

Perceptible 
fig. 

Good  fig. 

• 
Cucurbita  Pepo  

Nights    days 
o 

0 

o 
o 

0 
2                I 

3   •        2 

Minutes 
IS 
30 
30 
20 

20 
SO 
3<> 

Minutes 
So 

120 
120 
90 
60 
90 
120 

Minutes 
4-iS 
5 
5 
5 
5-iS 
i 

5 

Hdianthus  annuus  
Impatiens  Sultani 

Phaseolus  vulgaris  
Ricinus  communis  
Trop&olum  ma  jus  
Zea  Mais  

48 


THE  DIGESTION   OF   STARCH  49 

3.  Name  two  advantages  to  the  plant  of  this  new 
process  you  have  studied. 

4.  The  changing  of  an  insoluble  substance  to  a  soluble 
one  and  dissolving  it  is  digestion. 

5.  Briefly    enumerate,    in    order,    using    the    proper 
scientific  terms,  the  processes  that  you  have  learned 
take  place  in  a  green  leaf  from  sunrise  to  sunrise 
again. 

B.  Conversion  of  Starch  to  Sugar'. 

Experiment  32. — To  see  if  starch  may  be  digested 
to  sugar  by  an  enzyme. 

1.  Into  a  test-tube  one-half  full  of  a  dilute  starch 
mixture  place  several  drops  of  iodine. 

2.  Add  to  this  mixture  a  few  drops  of  a  solution  of 
diastase. 

3.  At  intervals  of  fifteen  to  twenty  minutes  test  for 
sugar.    Describe  all  color  changes  observed  through- 
out the  experiment. 

C.  State  with  special  care  and  detail  the  inferences  warranted 
by  experiments  31  and  32.1 

1  NOTE:  The  study  of  proteins  and  fats  is  here  omitted,  not  being  con- 
sidered essential  in  an  introductory  course. 


XIII.  ALCOHOLIC  FERMENTATION 

A.  The    development   of   heat    by    alcoholic    fermentation: 

1.  In  these  experiments  fresh  compressed  yeast  may 
be  used,  and,  for  a  fermenting  substance,  either 
commercial  molasses  (20  c.c.)  in  water  (100  c.c.), 
or  Pasteur's  solution,  made  up  as  follows: 

Pasteur's  Fermentation  Solution 

Grape  sugar 150  c.c. 

Ammonium  tartrate. 10  c.c. 

Magnesium  sulphate 2  grams 

Calcium  phosphate 2  grams 

Potassium  phosphate 2  grams 

Distilled  water 838  c.c. 

Experiment  33. — To  ascertain  what  temperature  change 
accompanies  alcoholic  fermentation. 

2.  Place  about  5  grams  of  compressed  yeast  in  250 
c.c.  of  the  Pasteur's  solution,  shake  well,  and  pour 
into  a  Dewar  flask. 

3.  Place  a  similar  amount  of  distilled  (or  tap)  water 
in  a  second  flask. 

4.  Record  the  temperatures  of  both  liquids  at  once, 
using  two  thermometers  which  should  remain  in 
the   liquids   until   the   experiment  is  over.1    The 
experiment  will  work  best  if  the  liquids  are  at 
about  25°C. 

1  The  instructor  will,  of  course,  understand  the  necessity  of  carefully 
comparing  the  initial  readings  of  the  thermometers,  where  two  or  more  are 
used,  and  of  making  necessary  corrections  in  subsequent  readings. 

So 


ALCOHOLIC   FERMENTATION  51 

5.  Set  the  two  Dewar  flasks  side  by  side  where  they 
will  not  be  subject  to  great  or  unequal  changes 
of  external  temperature. 

6.  At  frequent  intervals  (e.g.,  twenty  minutes)  during 
the  next  two  hours,  record  the  temperatures  of 
the  two  fluids.     Continue  the  records  over  as  long 
a  period  as  convenient,  not  exceeding  twenty-four 
hours. 

7.  Tabulate  the  results,  and  from  the  figures  con- 
struct two  "curves/'  showing  the  rate  and  amount 
of  temperature  change  in  each  flask. 

8.  State  your  inferences  from  this  experiment. 
B.  The  gaseous  exchange  in  alcoholic  fermentation: 

Experiment  34. — To  ascertain  what  gaseous  exchange 
accompanies  alcoholic  fermentation. 

1.  Place  250  c.c.  of  fermenting  mixture  into  a  tall 
glass  cylinder,  and  250  c.c.  of  distilled  water  into 
a    similar    adjacent    cylinder,    as    a    control.    At 
once  test  the  air  in  the  cylinders  above  the  liquid 
with  lime  water,  to  see  if  the  latter  turns  milky, 
as  a  result  of  the  formation  of  a  precipitate  of 
carbonate  of  lime.1 

2.  After  the  test  for  CO*,  test  the  air  in  both  cylinders 
with  a  lighted  splinter  or  taper,  to  see  if  it  contains 
sufficient    oxygen    to   support   combustion.    The 
taper  should  be  rapidly  lowered  into  and  removed 
from  the  cylinder.     Why? 

1  If  the  members  of  the  class  are  not  familiar  with  the  effect  of  COS  on 
lime  water,  this  should  be  demonstrated  by  the  instructor,  using  both 
chemically  prepared  COj  and  the  breath  from  the  lungs,  before  proceeding 
with  the  experiments  in  fermentation  and  respiration. 

The  air  in  the  cylinder  may  conveniently  be  tested  by  first  dipping  a 
small  wire  loop  (e.g.,  10  mm.  in  diameter)  into  lime  water.  A  film  of  the 
lime  water  will  form  across  the  loop,  and  may  thus  be  transferred  into  the 
cylinder. 


52  ANATOMY  AND  PHYSIOLOGY 

3.  Place  a  greased  glass  plate  over  each  cylinder,  or 
close  the  cylinders  with  a  rubber  stopper,  and  after 
an  interval  of  about  one  hour  (at  a  temperature 
of  about  25°C.)  repeat  the  tests  for  0  and  C02. 
Test  again  after  two  or  more  hours. 

4.  Record  and  interpret  your  results,  especially  dis- 
cussing any  circumstances  that  may  have  operated 
to  affect  the  progress  of  the  experiment  either  favor- 
ably or  unfavorably. 

C.  The  Formation  of  Alcohol  Demonstrated: 

Experiment  35. — To  test  for  the  presence  of  alcohol. 

1.  After  the  fermentation  in  the  last  experiment  has 
proceeded  for  twenty-four  hours,  distill  about  150 
to  200  c.c.  of  the  fermenting  liquid,  and  redistill  the 
first  distillate. 

2.  Test  a  portion  of  the  second  distillate  with  a  flame 
to  see  if  it  will  burn.     If  it  will,  describe  and  explain 
the  result. 

3.  The  presence  of  alcohol  may  also  be  tested,  in 
either  the  first  or  the  second  distillate,  by  adding  to 
it  several  drops  of  a  mixture  composed  of  a  strong 
aqueous  solution  of  bichromate  of  potash,  to  which 
have  been  added  a  few  drops  of  sulphuric  acid.     If 
a  green  color  results,  the  presence  of  alcohol  is 
indicated. 

4.  Briefly  summarize   the  products  of  alcoholic   fer- 
mentation, ascertained  by  the  above  experiments. 
From  where  did  these  products   come,  and  what 
was  the  active  agent  in  their  formation? 


XIV.  RESPIRATION 

A.  Anaerobic  Respiration: 

Experiment  36. — To  illustrate  anaerobic  respiration. 

1.  Remove  the  seed-coats  from  three  or  four  pea  seeds 
that  have  soaked  in  water  over  night. 

2.  Fill   a   large   glass   test-tube   with   mercury,   and 
invert  it  in  a  bath  of  mercury. 

3.  Place  the  pea  Seeds  under  the  mouth  of  the  inverted 
test-tube,  and  allow  them  to  float  to  the  top.     Use 
every  possible  precaution  to  prevent  air  being  car- 
ried up  with  the  peas.     Can  the  presence  of  air 
be  entirely  prevented? 

4.  Securely  fasten  the  test-tube  in  the  inverted  posi- 
tion, with  its  mouth  under  the  surface  of  the  mer- 
cury in  the  bath,  and  during  the  next  twenty-four 
to    forty-eight    hours    observe    the    formation    of 
gas,  which  replaces  the  mercury  around  the  seeds. 

5.  Now  introduce  in  to  the  test-tube  with  the  pea  seeds 
a  small  piece  of  potassium  hydroxide.    If  the  gas 
given  off  by  the  seeds  is  COz  it  will  be  absorbed  by 
the  potassium  hydroxide,  and  the  mercury  will  rise 
in  the  tube. 

6.  Do  these  seeds  respire  under  strictly  anaerobic  con- 
ditions?   Discuss,  iny  our  note-book,  all  the  pros 
and  cons,  and  endeavor  to  make  a  clear  statement 
of  just  what  this  Experiment  does  and  does  not 
demonstrate. 

B.  Aerobic  Respiration: 

Experiment  37. — To  demonstrate  what  exchange  of 
gases  accompanies  the  aerobic  respiration  of  a  living 
plant. 

S3 


54  ANATOMY  AND   PHYSIOLOGY 

1.  Place  a  vigorous  potted  plant  on  a  ground-glass 
plate.     By  the  side  of  it  place  a  watch-glass  full  of 
lime  water,  or  baryta  water;  over  all  place  a  glass 
bell-jar  with  a  large  tubulature  at  the  top. 

2.  Make  the  joint  between  the  bell-jar  and  the  ground- 
glass  plate  air-tight  by  means  of  vaseline. 

3.  Test  the  air  in  the  jar  with  a  lighted  taper  to  be  sure 
that  it  contains  enough  oxygen  to  support  combus- 
tion. 

4.  Insert  a  rubber  stopper  into  the  tubulature  so  as 
to  make  it  air-tight,  and  set  the  plant  aside,  in  a 
dark  place.     Why? 

5.  At  the  next  laboratory  period  (preferably  on  the 
following  day),  and  without  disturbing  the  bell-jar, 
observe  the  color  of  the  lime  water  in  the  watch- 
glass.    What  does  it  indicate? 

6.  Quickly  and  cautiously  insert  a  lighted  taper  into 
the  bell-jar  through  the  tubulature.     What  results? 
What  inference  is  justified? 

Experiment  38. — To  see  if  all  parts  of  a  plant,  and  non- 
green  plants,  respire. 

7.  Take  six  cylindrical  glass  jars,  a,  b,  c,  d,  e,  and  /, 
provided  with  air-tight  rubber  stoppers. 

8.  Into  (a)  place  a  quantity  of  green  leaves;  into  (b) 
green  stems  of  some  herb;  into  (c)  young  clean 
roots  of  some  herb;  into  (d)  freshly  picked  flowers; 
into  (e)  one  or  two  fresh  fleshy  fungi;  and  into  (/") 
nothing.     Confine  the  plant  material  to  one  side 
of  the  jars  by  inserting  a  vertical  partition  of  coarse 
wire  netting. 

9.  Test  the  air  in  each  jar  to  be  sure  that  it  will  sup- 
port combustion,  then  cork  the  jars  air-tight,  and 
place  them  in  a  convenient  place. 

10.  At  the  next  laboratory  period  carefully  test  the  air 


RESPIRATION  55 

in  each  jar  with  the  burning  taper.     What  infer- 
ence may  be  drawn  from  the  result? 

11.  Next,  pour  into  each  jar  a  bit  of  clear  lime  water, 
and  wash  the  air  by  tipping  the  jars  back  and  forth, 
holding  the  half  containing  the  plant  material  upper- 
most.    What  conclusion  does  the  result  justify? 

12.  Clearly  state  the  general  conclusion  from  this  ex- 
periment. 

C.   The   Temperature  Change  Accompanying  Plant  Res- 
piration : 

Experiment  39. — To  ascertain  what  temperature  change 
accompanies  the  respiration  of  germinating  seeds. 

1.  Place  a  quantity  of  germinating  seeds  (e.g.,  oats, 
wheat,  lupine)  into  a  Dewar  flask.     Into  a  second 
Dewar  flask  place  nothing. 

2.  Into  each  flask  insert  a  thermometer  (being  sure 
first  to  compare  their  readings).     The  bulb  of  the 
thermometer   in    the    flask    containing    the    seeds 
should  be  well  covered  by  them.     Place  the  flasks 
where  they  will  not  be  subject  to  great  nor  unequal 
changes  of  external  temperature. 

3.  After    twenty-four   hours  record  the  temperature 
indicated  by  each  thermometer. 

4.  Thoughtfully  discuss  and  interpret  the  results  ob- 
served. 

5.  Compare  the  process  of  fermentation  with  that  of 
respiration.    What  inference  is  suggested  by  this 
comparison  as  to  the  real  nature  of  respiration? 


XV.  THE  INFLUENCE  OF  EXTERNAL  CONDITIONS  ON  THE 

PLANT 

A.  The  Influence  of  Gravity  on  the  Direction  of  Growth: 
Experiment  40. — To  find  how  gravity  affects  the  direc- 
tion of  growth  of  roots  and  shoots. 

1.  Choose  two  or  three  young  seedlings  of  the  pumpkin 
or  lupine,  with  radicles  about  10  mm.  long. 

2.  Pin  the  seedlings  horizontally  on  a  cork  and  place 
in  a  moist  chamber  in  the  dark  (why  in  the  dark?) 
until  the  next  period.    A  Petri  dish  will  furnish  a 
simple  moist  chamber. 

3.  Make  a  drawing  of  the  seedlings  in  the  horizontal 
position. 

4.  At  the  next  laboratory  period  observe  the  position 
of  both  root  and  shoot.     Draw. 

5.  Do  the  results  give  any  evidence  that  the  root  grew 
downward  and  was  not  pulled  down  by  gravity? 
Explain. 

B.  Influence  of  Light  on  the  Rate  of  Growth  of  Stems: 

1.  Compare  the  lengths  of  the  stems  of  seedlings  of  the 
same  age  that  have  grown,  one  in  the  dark,  the  other 
in  the  light.     State  the  exact  length  of  each  of  the 
stems  in  centimeters. 

2.  What  do  you  infer  is  the  effect  of  light  on  the  rate 
of  growth  of  stems  of  the  plants  observed? 

3.  Do  you  think  this  is  true  of  all  plants?  (This  point 
should  be  discussed  with  the  instructor,  in  the  light 
of  more  recent  investigations  on  the  subject.     See 
especially,  MacDougal,  "The  Effects  of  Light  and 

5<5 


INFLUENCE  OF  EXTERNAL  CONDITIONS  ON  THE  PLANT         57 

Darkness  on  Growth  and  Development."    Memoirs 
of  the  New  York  Botanical  Garden,  No.  3.) 
C.  The  Influence  of  Light  on  the  Direction  of  Growth  of  Roots 

and  Stems: 

Experiment  41. — To  ascertain  how  one-sided  illumina- 
tion affects  the  direction  of  growth  of  roots  and 
stems. 

1.  Fix  a  vigorous  young  seedling  of  white  mustard 
with  the  root  extending  through  the  mesh  of  a  piece 
of  cheese-cloth  stretched  over  the  mouth  of  a  large 
salt-mouthed  bottle  nearly  filled  with  tap-water. 
The  seedling  should  be  as  straight  as  possible,  and 
stand  vertically  at  the  beginning  of  the  experiment, 
with  root  extending  well  into  the  water. 

2.  Place  the  plant  thus  prepared  into  a  box  with  a 
tightly  fitting  cover  and  a  narrow,  vertical  slit  at 
one  side  to  admit  the  light.     (A  pasteboard  shoe- 
box  with  the  cover  on,  and  the  slit  cut  vertically 
in  the  cover  will  answer.) 

3.  Set  the  box  and  plant  in  a  well-lighted  window, 
with  the  slit  toward  the  light. 

4.  Make  a  diagram  of  the  entire  apparatus  and  plant, 
in  longitudinal  section. 

5.  At  the  next  laboratory  period  carefully  remove  the 
cover  from  the  box  and  observe  the  position  of  the 
root  and  stem. 

6.  Draw  another  diagram  similar  to,  and  by  the  side 
of  the  first  one,  showing  what  you  observe. 

7.  Compare  the  manner  of  response  of  the  root  and 
stem  to  one-sided  illumination. 


PART  II 

MORPHOLOGY  AND  LIFE  HISTORY 


I,  MEANING  pr  THE  TERMS 

A.  Morphology. — Under   Part   I   we   considered   various 
physiological  processes,  the  primary  result  of  which  was 
to  maintain  the  life  of  the  individual  plant.     Most  of 
those  processes  were  found  to  be  carried  on  by  all 
plants.     It  is  common  knowledge,  however,  that  plants 
differ  widely  from  each  other  in  both  structure  and 
habit  of  life.     In  other  words,  we  recognize  the  fact  of 
variation.    This  means  that  different  plants  solve  the 
same  problems  of  life  in  different  ways.    That  phase  of 
botany  which  concerns  itself  with  a  comparative  study 
of  structures,  and  seeks  to  interpret  the  structural  value 
of  an  organ,  no  matter  how  it  may  be  disguised,  is 
termed  the  science  of  form,  or  morphology. 

B.  Life  History. — Every  plant,  in  the  course  of  its  exist- 
ence, passes  through  a  series  of  changes,  in  orderly 
sequence.    Like  an  animal,  every  plant  begins  life  as 
a  single  cell,  the  egg,  or  the  equivalent  of  an  egg; 
the  egg  (except  in  some  of  the  lower  plants)  develops 
into  an  embyro,  and  the  embryo  grows  and  develops 
into  an  adult.     The  adult  in  turn,  produces  an  egg, 
like  the  one  from  which  it  came,  thus  completing  one 
life   cycle    and    initiating    another.     These    various 
changes  constitute  the  life  history  of  the  individual. 

59 


60  MORPHOLOGY  AND   LIFE   HISTORY 

C.  Descent. — Just  as  one  of  the  higher  plants,  such  as  a 
maple  tree,  begins  life  as  a  single  cell,  and  becomes 
more  and  more  complex  as  it  matures,  so  the  plant 
kingdom  as  a  whole,  presents  us  with  a  series  of  organ- 
isms of  gradually  increasing  complexity  from  the  sim- 
plest one-celled  forms  to  myriad-celled,  complex  forms. 
This  fact  suggests  that  the  entire  plant  kingdom,  like 
every  individual  plant,  has  had  a  developmental  his- 
tory, the  more  complex  organisms  being  derived  from 
more  simple  ones  by  a  series  of  gradual  changes.    This  is 
the  theory  of  descent,  or  organic  evolution.    It  teaches 
us  that  all  organisms  are  related  to  each  other,  and 
is  one  explanation  of  why  we  so  often  find  the  same 
organ  appearing  again  and  again,  under  various  guises, 
in  plants  externally  unlike. 

D.  Classification. — The    study   of   morphology   and   life 
histories  enables  us  to  recognize  relationships  among 
plants,  and  hence  to  build  up  a  genealogical  tree, 
showing  lines  of  descent.    Thus  we  can  arrange  plants, 
together  with  their  nearest  relatives,  in  groups;  and 
related  groups,  again,  in  larger  groups  of  successively 
higher  orders.     This  gives  us  a  rational  basis  for  the 
classification  of  plants,  and  this  phase  of  plant  study 
is  called  systematic  botany,  for  it  makes  possible 
the  arrangement  of  plants  into  a  system,  which  en- 
deawrs  to  show  how  the  plant  kingdom,  in  all  its  diversity, 
has  developed,  or  evolved.    This  greatly  simplifies  our 
study  of  plants,  for  the  number  of  different  plants  is  too 
great  for  us  to  study  every  one;  but  if  we  recognize 
that  each  plant  more  or  less  imperfectly  illustrates 
a  group,  then  we  can  study  an  illustration  of  each 
group,  and  thus  get  a  more  nearly  adequate  picture 
of  the  kingdom  of  plants  as  a  whole.     The  various 
systematic  groups  are  given  in  E  below. 


MEANING   OF  THE   TERMS 


6l 


E.  An  Outline  of  the  Classification  of  Plants:1 
THE  GREAT  GROUPS  OF  PLANTS 


Division 


I.  Thallophyta.. 


Subdivision 


A.  Algae. 


B.  Fungi. 


Class 

1.  Cyanophyceae 

2.  Chlorophyceae 

3.  Phaeophyceae 

4.  Rhodophyceae 

1.  Myxomycetes 

2.  Schizomycetes 

(Bacteria) 

3.  Phycomycetes 

4.  Ascomycetes 

5.  Basidiomycetes 

6.  Fungi  imperfecti 

(life  histories 
imperfectly  known) 


Order 


II.  Bryophyta. 


III.  Pteridophyta.. 


IV.   Calamophyta. 
V.  Lepidophyta. 


VI.   Cycadophyta. 


z.  Hepaticae 


2.  Musci 

1.  Eusporangiatse. .  .  . 

2.  Leptosporangiatae., 

r.  Sphenophyllineas, . 

2.  Equisetineae 

3.  Calamarineas 

1.  Lycopodineae 

f.  Lepidodendrineae.. 
\ 

f  i.  Cycadofilicineae.  .  . 

2.  Cycadineae 

3.  Bennettitineae 


4.   Cordaitineae.. . 


f  Ricciales 
I    Marchantiales 
|  Jungermanniales 
[  Anthocerotales 

Andreales 

Sphagnales 

Bryales 

Ophioglossales 

Marratiales 

Isoetales 

Filicales 

Marsiliales 

Sphenophyllales 

Equisetales 

Calamarales 

Lycopodiales 

Selaginellales 

Lepidodendrales 

Cycadofilicalea 

Cycadales 

Bennettitales 

Cordaitales 

Ginkgoales 

Gnetales 


1  For  reference,  not  memorizing. 


62 


MORPHOLOGY  AND   LIFE   HISTORY 


THE  GREAT  GROUP  OF  PLANTS — (Continued) 

Division  Subdivision  Class  Order 


VII.  Spermatophyta 


A.  Gymno- 
sperma 


Pinoideae. 


B.  Angio- 

spermae 


I.   Monocotyledoneae 


2.  Dicotyledonese. . 


(a)  Archichlamydeae 
Apetalae 
Polypetalae 


(&)    Metachlamydeae 
Sympetalse  (=- 
Gamopetalae) 


Coniferales 
Taxales 
Pandanales 
Naidales 
Graminales 
Arales 
X  yridales 
Liliales 
Scitamnales 
Orchidales 
.32  Orders,  including 
'  Salicales 
Polygonales 
Ranunculales 
Resales 
Violales 
Myrtales 
Umbellales 
Ericales 
Polemoniales 
Plantaginales 
Rubiales 
Campanulales 


2.  DIRECTIONS  FOR  STUDY 

Polypodium  vulgare  (COMMON  POLYPODY) 

A.  Classification: 

Division  III.     Pteridophyta  (fern  plants). 
Class  I.    Leptosporangiatae. 
Order.     Filicales. 

Family.    Polypodiaceae. 
Genus.    Polypodium. 
Species,    vulgare. 

B.  Habitat: 

i.  Record  here  your  knowledge  of  the  habitat  of  the 
specimen  studied.  The  information  is  to  be  ob- 
tained from  your  own  observation,  and  from  your 
reading  and  class  work. 

THE  "FERN  PLANT" 

C.  Naked-eye  Characters: 

1.  General  features. 

(a)  Note  that  the  sporophyte  is  differentiated 
into  root  and  shoot. 

(6)  The  leaf  portion  of  the  shoot  is  often  called  the 
frond.  The  fibrous  roots  and  the  leaves  are 
borne  on  an  underground  stem  (rhizome). 

(c)  Make  a  sketch  of  the  entire  sporophyte  (in- 
cluding only  one  leaf). 

2.  The  rhizome. 

(a)  Describe  the  natural  attitude   (i.e.,  erect,  or 
horizontal)    of    the    rhizome.     Where    does   it 
63 


64  MORPHOLOGY  AND   LIFE  HISTORY 

grow?    If   it   branches,    describe   its   manner 
of  branching. 

(b)  Does  the  rhizome  bear  any  outgrowths  besides 
the  leaves  and  roots?    If  so,   describe  their 
structure,  color,  relative  number,  and  location. 

(c)  The  places  on  the  rhizome  where  the  leaves  are 
borne  are  called  nodes.    What  is  the  region 
between  two  nodes  called? 

Note. — The  directions  below  (d-i)  apply  especially  to 
the  bracken  fern,  Pteris  aquilina. 

(d)  Observe   the  end  of  a  rhizome  cut  squarely 
across.     If  preserved  material  is  used,  the  cut 
surface  should  be  kept  moistened  during  the 
study.     The  observations  may  best  be  made 
from  a  piece  5  to  10  mm.  thick,  cut  transversely 
and  placed  in  a  watch-glass  of  water.    Do  not 
cut  or  injure  you  specimen  in  any  way,  as  it 
will  be  collected  for  further  preservation  at  the 
end  of  the  study. 

(e)  Distinguish  the  following  tissue-regions: 

(1)  The  epidermis  (black  in  preserved  material) . 

(2)  Underneath  the  epidermis  a  narrow,  dark- 
colored  region  of  hypodermal  sclerenchyma. 

(3)  Within  the  hypodermal  sclerenchyma  the 
fundamental  tissue  (parenchyma). 

(4)  Imbedded  in  the  parenchyma  two  promi- 
nent elongate,  dark-colored  areas,  the  central 
sclerenchyma,  or  stereome  (sometimes  fused 
into  one). 

(5)  Also  imbedded  in  the  parenchyma,  and  sur- 
rounding the  inner  sclerenchyma,  several 
areas  of  fibre-vascular  bundles.    In  fresh 
specimens   these   areas   are   yellowish,   in 
preserved  material  they  are  lighter  colored 


DIRECTIONS   FOR   STUDY  65 

than  the  inner  sclerenchyma.  How  do 
they  appear  when  a  section  is  held  to  the 
light? 

(/)  Identify  all  the  areas  referred  to  above  (e,  1-5) 
in  a  longitudinal  section  of  the  rhizome. 

(g)  At  home,  write  a  well- worded  description  of 
your  observations  under  e  and  /. 

(ti)  Make  a  diagram,  10  cm.  in  longest  diameter, 
showing  carefully  the  outline  of  the  rhizome  as 
seen  in  cross-section,  and  all  the  tissue-regions 
identified.  Label  each  region,  and  underneath 
your  drawing  indicate  the  amount  of  enlarge- 
ment. 

(i)  Underneath  the  first  diagram  make  a  second 
one,  of  the  same  enlargement,  showing  the  rela- 
tion of  the  tissues  of  the  rhizome  as  seen  in 
longitudinal  section. 

3.  The  roots. 

(a)  Describe  the  location,  form,  length,  diameter, 
branching,  relative  number,  and  relation  to 
each  other  (i.e.,  close  together  or  not;  inter- 
woven or  not)  of  the  roots.  Draw. 

4.  The  leaves. 

(a)  On  what  surface  of  the  rhizome  are  the  leaves 
borne? 

(b)  Note  their  differentiation  into  stem-like  part, 
the  petiole,  and  expanded  portion,  the  blade. 

(c)  What  is  the  color  of  the  leaf?    Describe  and 
suggest  a  probable  reason  for  any  differences  in 
color. 

(d)  Is  the  petiole  glaucus  (smooth,  without  hairs), 
or  pubescent  (hairy)  ? 

(e)  Is  the  blade  entire,  or  divided  into  pinnae?    If 
the  latter,  do  the  clefts  between  the  pinnae  ex- 


66  MORPHOLOGY  AND   LIFE   HISTORY 

tend  clear  to  the  midrib?  Compare  the  basal 
with  the  more  distal  clefts  in  this  respect. 

(0  Do  the  pinnae  appear  to  be  all  of  the  same  age? 
If  not,  state  reasons  for  considering  some  of 
them  younger  than  others.  Find  evidence  in 
your  specimen  of  the  method  of  formation  of 
the  pinnae.  Are  they  opposite  or  alternate? 

(g)  Describe  and  compare  the  venation  of  the  blade, 
and  of  the  individual  pinnae.  Describe  any 
constant  relationship  between  the  venation  and 
manner  of  branching  of  the  blade. 

(ti)  Do  the  smaller  veins  anastomose  (i.e.,  have  their 
ends  united  so  as  to  form  a  network),  or  are 
their  ends  free?  Compare  the  fern  leaf  in  this 
respect  with  the  foliage-leaf  of  a  seed-bearing 
plant. 

(i)  Describe  the  appearance  of  very  young,  unex- 
panded  leaves  or  portions  of  leaves. 

(k)  On  the  ventral  surface  of  some  of  the  leaves  find 
the  brownish  fruit-dots,  or  son  (sing,  sorus). 
Describe  their  location.  Do  you  find  them  on 
the  midrib  of  the  frond  or  on  the  individual 
pinnae?  Are  they  between  the  smaller  veins  or 
on  them?  If  the  latter,  on  what  part  of  the 
vein?  Is  their  position  constant  (i.e.,  always 
the  same)?  Are  they  located  at  the  margin  of 
the  frond  or  pinna,  or  back  from  the  margin? 
Describe  their  shape. 

(/)  Do  the  sori  occur  on  all  the  pinnae  of  a  leaf? 
On  all  the  leaves?  Compare  several  specimens 
with  reference  to  this  point. 

(m)  Observe,  using  hand  lens  if  necessary,  that  the 
sorus  is  composed  of  a  group  of  small  organs 
(sporangia).  What  do  sporangia  produce? 


DIRECTIONS   FOR   STUDY  67 

(n)  Is  there  a  membranous  expansion  (indusium) 
covering  the  sporangia  in  your  specimen?  Ex- 
amine fronds  of  the  other  species  of  fern  dis- 
played in  the  laboratory  and  record  your  obser- 
vations on  this  point,  stating  the  names  of  the 
species  observed. 

(0)  Leaves  bearing  spores  are  sporophylls.  Fern 
leaves  that  do  not  bear  spores  are  vegetative 
leaves  or  foliage -leaves. 

(p)  Do  some  of  the  sporophylls  also  function  as 
foliage-leaves? 

(q)  Examine  specimens  of  other  kinds  of  ferns  ex- 
hibited in  the  laboratory  and  see  if  your  answer 
to^(p)  is  true  of  all  ferns.  Describe  briefly  any 
exceptions  found,  giving  the  name  of  the  fern. 

(r)  Make  drawings,  natural  size,  illustrating  all 
features  of  the  frond  not  clearly  shown  in  your 
first  sketch. 

D.  Microscopic  Characters: 
i.  The  rhizome. 

(a)  Study  prepared  slides  of  cross-sections  of  the 
rhizome.     (Pteris  aquilina  is  suggested  as  spec- 
ially satisfactory  for  this  study,  a-g.) 

(b)  With  the  low  power  survey  the  section  and 
identify  the  various  tissue-regions  already  dis- 
tinguished. 

(c)  With  the  high  power,  study  the  epidermis,  and 
describe  how  many  cells  it  is  in  thickness,  the 
variation  in  thickness   of   the  cell-walls,   the 
middle  lamella,  separating  the  adjacent  cells, 
and  the  canals,  or  channels,  extending  from  the 
cell-cavity  outward  through  the  cell-wall.     Do 
these  canals  ever  branch?    Do  they  form  a 


68  MORPHOLOGY  AND   LIFE   HISTORY 

network?     Is   there   any   connection  between 
the  cell-cavities  of  adjacent  cells? 

(d)  In  a  similar  manner  examine  the  cellular  struc- 
ture of  the  hypodermal  sclerenchyma. 

(e)  Make  drawings  illustrating   the  features   ob- 
served in  (c)  and  (d),  showing  four  cells  of  the 
epidermis,  and  three  or  four  of  the  underlying 
sclerenchyma-cells.     The  cells  should  not  be 
less  than  10  to  15  mm.  in  diameter. 

(/)    Make  similar  studies  and  drawings  of  the  cells 

of  the  parenchyma. 
(g)  Study  one  of  the  smaller  fibre-vascular  bundles 

and  distinguish,  from  the  circumference  toward 

the  center: 

(1)  The  outer  bundle-sheath,  or  endodermis. 

(2)  Within  the  endodermis,  and  adjacent  to  it, 
a  single  layer  of  starch-bearing  parenchy- 
ma tous  cells,  the  phloem -sheath. 

(3)  Thick- walled  bast-fibers. 

(4)  Larger,  thin- walled  cells,  having  their  cell- 
walls  perforated,  the  sieve-tubes. 

(5)  Associated   with    the    cells    mentioned   in 
(2)-(4),  parenchyma-cells  (phloem-paren- 
chyma), containing  starch. 

(6)  The  cells  mentioned  in  (3)-($)  constitute 
the    phloem-region,    of    the    bundle,    or 
phloem. 

(7)  Within  the  phloem  is  the  xylem-region,  or 
xylem,  composed  of 

(8)  Large,  conspicuous  tracheids,  whose  walls 
have  ladder-like  (scalariform)  markings  as 
seen   in   longitudinal   section.     Each   tra- 
cheid  is  a  tube,  filled  with  air,  and  formed 


DIRECTIONS   FOR   STUDY  69 

by  the  fusion  of  several  cells  through  the 

disappearance  of  their  end  walls. 
(9)  Smaller  sieve-tubes,  resembling  those  of 

the  phloem. 
(10)  Thin-walled   cells  forming  the  wood-,   or 

xylem-parenchyma . 
(n)  Since    the    tissues    of    the    nbro-vascular 

bundles  are  arranged  circularly  about  a 

common    center,    the    bundle    is  called  a 

concentric  bundle. 

(12)  Compare  the  various  bundles  and  see  if 
they  are  all  of  similar  structure. 

(13)  Make    a    careful    drawing    showing    the 
structure  of  the  bundle,  including  all  points 
mentioned  under  (g),  (i)-(io).     This  draw- 
ing should  be  at  least  75  mm.  in  longest 
diameter. 

2.  The  pinna. 

(a)  Under  the  low  power  examine  a  small  portion  of 
one   of  the  pinnae  or  pinnules  not  bearing  a 
sorus,   and  note  the  presence  or  absence  of 
outgrowths. 

(b)  Can  you  observe  any  veins  too  small  to  be  seen 
with  the  naked  eye?    If  so,  describe  their  re- 
lation to  each  other. 

(c)  Mount  a  small  bit  of  the  lower  epidermis,  and 
describe  (a)  any  outgrowths;  (b)  the  stomata 
and  guard-cells,  stating  the  number,  shape, 
and  contents  of  the  latter.     Describe  the  rela- 
tive number  and  distribution  of  the  stomata. 

(d)  Compare  the  stomata  of  the  fern  with  those  of 
a  seed-bearing  plant. 

(e)  Make   drawings   showing   all   features   shown 
under  2,  (b)-(d). 


70  MORPHOLOGY  AND   LIFE   HISTORY 

(/)  Describe  a  cross-section  of  a  pinna  as  shown  in 
a  prepared  slide.     Draw.     Compare  its  struc- 
ture with  that  of  a  foliage-leaf  of  a  higher  plant. 
E.  Non-sexual  Reproduction: 

1.  Describe  the  possibilities  of  vegetative  propagation 
of  the  sporophyte. 

2.  With  a  needle  remove  several  sporangia  from  a 
sorus,  mount  them  in  water  and  study  under  low 
power. 

3.  Observe  the  differentiation  of  the  sporangium  into 
a  stalk   (pedicle),   and  a  spore-case,   containing 
spores.     Note  the  walls  of  the  spore-case,  and  the 
row  of  thickened  cells,  the  annulus.     Describe  these 
cells.     Note  the  special  opening  in  the  spore-case, 
through   which    the    spores    escape   between    the 
lip-cells. 

4.  Make  a  drawing  of  the  sporangium,  about  35  mm. 
in  shortest  diameter,   showing  a  portion  of   the 
pedicle. 

5.  Study  the  shape  and  surface  markings,  if  any,  of 
a  single  spore.    Account  for  the  shape.    Are  they 
all  of  substantially  the  same  size,  i.e.,  is  Poly  podium 
a  homosporus  pteridophyte? 

6.  Make  a  drawing  of  the  spore  15  mm.  in  longest 
measure. 

7.  Run  a  drop  of  glycerine  under  the  cover-glass  and 
carefully  watch  for  the  snapping  motion  of  the 
sporangia   by  which,   in   nature,    the   spores   are 
expelled. 

8.  Explain  the  advantage  to  the  species  of  having  the 
spores  expelled.     Why  would  it  not  be  as  well  if 
they  merely  dropped  out  of  the  spore-case? 
9.  If  suitable  material  is  at  hand,  study  stages  in  the 
germination  of  the  spores. 


DIRECTIONS   FOR   STUDY  71 

10.  To  which  of  the  alternating  generations  does  the 
fern-plant  belong?     Why? 

11.  Into  what  does  the  spore  develop? 

THE  PROTHALLUS 

F.  Habitat: 

i.  State  the  locations  and  conditions  of  growth  of  the 
prothallus  (also  called  prothallium),  (a)  in  artificial 
culture;  (b)  in  nature. 

G.  Naked-eye  Characters: 

1.  Describe  the  exact  size  (in  millimeters),  color,  and 
shape  of  the  prothallus. 

2.  It  is  differentiated  into  a  dorsal  and  a  ventral  sur- 
face?    If  so,  how  are  the  two  surfaces  distinguished? 

3.  Describe  the  location  and  character  of  the  rhizoids. 
H.  Microscopic  Characters: 

1.  Mount  a  prothallus  in  water  or  clearing  fluid,  ven- 
tral side  up,  under  a  cover-glass. 

2.  Describe  the  structure  and  contents  of  the  cells. 

3.  Describe  variations  in  thickness.     Do  you  find  a 
thicker  central  portion,  or  cushion? 

4.  Observe  the  growing  point  in  the  notch. 

5.  Study  the  location  and  character  of  the  rhizoids. 
Are  cross- walls  present? 

7.   Sexual  Reproduction: 

1.  Among  the  rhizoids  find  small,  spherical  elevations, 
the  antheridia.    Describe  their  number  and  dis- 
tribution. 

2.  Nearer  the  notch  observe  the  archegonia,  appearing 
to  be  composed  of  four  cells,  surrounding  an  opening 
or  canal. 

3.  Make  a  drawing,  at  least  5  cm.  in  longest  diameter, 
showing  all  features   of   the  prothallus   thus   far 


72  MORPHOLOGY  AND   LIFE   HISTORY 

observed.    By  the  side  of  this  figure  draw  an  out- 
line of  the  prothallus,  natural  size. 

4.  In  fresh  specimens  motile  antherizoids  or  sperms 
may  be  found  escaping  from  the  antheridia  and  swim- 
ming in  the  water.     If  these  are  found,  observe  the 
body  of  the  sperm  and  the  cilia.    How  many  cilia 
are  there?     Draw. 

5.  If  prepared  slides  are  supplied,  study  cross-sections 
of  the  prothallium  passing  through  an  antheridium 
and  an  archegonium.     Describe  accurately,  noting 
the  differentiation  of  the  archegonium  into  a  neck, 
containing  a  neck-canal,  and  a  venter,  containing 
an  oosphere  or  egg. 

6.  Make  a  diagram  of  the  section,  of  the  same  scale 
as  the  drawing  in  3  above,  and  make  drawings 
showing  details  of  structure  of  the  antheridia  and 
archegonia  as  seen  in  longitudinal  section. 

7.  To  what  class  of  reproductive  bodies  do  the  sperm 
and  egg  of  the  fern  belong?     To  which  of  the  alter- 
nating generations  does   the    prothallus    belong? 
Why?    Why  is  it  called  a  thallus? 

8.  Is  this  fern  monoecious  or  dioecious?    Explain. 

9.  What  structure  is  the  starting  point  of  the  sporo- 
phyte? 

10.  Diagram  the  life  history  of  the  fern  for  three  genera- 
tions, by  continuing  the  following  diagram;  letting 
G  =  gametophyte;  s  =  sperm;  e  =  egg;  S  =  sporo- 
phyte;  sp  =  asexual  spore: 


S-?,  etc. 


ii.  Make  a  diagram  to  show  the  life  cycle  of  the  fern, 
using  arrows  and  words,  arranged  in  a  circle. 


DIRECTIONS   FOR   STUDY 


73 


K,  Nutrition  and  Growth: 

1.  Is  photosynthesis  carried  on  by  both  gametophyte 
and    sporophyte?     Transpiration?    Absorption    of 
water  from  the  soil? 

2.  Explain  the  need  of  stomata  in  the  sporophyte.  Are 
they  present  in  the  gametophyte?     Explain. 

3.  Discuss  the  presence  or  absence  of  a  conducting 
system  in  the  pro  thallium  and  sporophyte. 

4.  Explain  how  the  presence  of  the  cushion  of  the  pro- 
thallium  is  related  to  the  needs  of  the  young  sporo- 
phyte. 

5.  Is  the  gametophyte  of  Poly  podium  ever  dependent 
upon  the  sporophyte  for  its  nutrition?     Its  exist- 
ence? 

L.  Comparison  of  Gametophyte  and  Sporophyte  of  Poly- 
podium: 
Copy  the  following  table  into  your  note-book,  and  mark 

x  after  the  word  gametophyte  or  sporophyte  in  the 

proper  column. 

TABLE  I 


i  8 
•a  c 

C  v 
>rH  In 

.H 

^o 

1 
R 

i.| 

"s-0 

*l 
ll 

ill 

c 

J3 

*«  X 

1 

^   (U 

2 

Generation 

Respiratio 

Photosynt 

Stomata 

Rhizoids 

I 

Capable  < 
pendent  e 

Partly  par 

^ 

^ 

1 

Bears  sex 
productiv 

Bears  ase 
productiv 

ii! 

Gametophyte.. 

Sporophyte  .  .  . 

Polytrichum  commune  (COMMON  HAIR-CAP  Moss)1 

A.  Classification: 

Division  II.     Bryophyta  (moss-plants). 
Class  II.     Musci  (mosses). 
Order.     Bryales. 
Family.    Polytrichaceae. 
Genus.    Polytrichum. 
Species,     commune. 

B.  Habitat: 

i.  Polytrichum  commune  is  widely  distributed,  growing 
in  the  soil  in  fields  and  woods. 

C.  Naked-eye  Characters: 

THE  GAMETOPHYTE  (THE  "MOSS-PLANT") 

1.  Note  that  there  are  two  kinds  of  leafy  "moss- 
plants."     The  one  having  the  cup-like  tip  is  the 
male  or  antheridial  plant;  the  other,  without  the 
cup-like  tip,   is  the  female,  or  archegonial  plant. 
Compare  the  average  height  of  the  mature  male 
and  female  plants.     Do  you  find  any  outgrowth 
from  the  tip  of  any  of  the  archegonial  plants? 

2.  Are   the  moss-plants  differentiated  into  root  and 
shoot?    Is   the   shoot   further   differentiated?     If 
so,  describe. 

3.  Briefly  describe  the  extent  and  ramifications  of  the 
"root"  system.    Are  these  true  roots,  with  root- 
hairs? 

4.  Briefly  describe  the  arrangement  of  the  leaves  on 

1  With  minor  modification  the  outline  here  given  for  the  study  of  the 
moss  will  serve  for  species  of  Mnium,  Funaria,  or  almost  any  other  com- 
mon moss. 

74 


POLYTRICHUM   COMMUNE  75 

the  stem  (opposite,  alternate,  spiral).  Are  the 
leaves  sessile  or  petiolate?  Simple  or  compound? 
Is  there  a  midrib?  Veins?  Compare  the  dorsal 
and  ventral  surfaces  of  the  leaves.  Describe 
any  variations  in  the  leaves  on  various  parts  of 
the  stem.  Describe  the  margin  of  the  leaf -blade 
(i.e.,  entire,  notched,  serrate,  etc.),  and  the  shape  of 
its  apex  and  base. 

5.  Compare  the  form  of  the  leaves  in  the  same  regions 
of  the  male  and  female  plants.     Note   especially 
the  rosette  of  perichsetse  (modified  leaves)  at  the 
summit  of  the  male  plant.     Compare  them  with 
the  foliage-leaves  below  them. 

6.  Describe  the  form  of  the  stem.     Is  it  of  uniform 
diameter?    Does  it  branch?     Compare  the  stems 
of  the  male  and  female  plants. 

7.  Make    suitable    drawings,    illustrating    all    points 
observed  under  C  1-6. 

THE  SPOROPHYTE 

8.  Select  an  archegonial  plant  with  sporophyte  (sporo- 
gonium)    attached.     Distinguish    the    long   stalk 
or  seta,  bearing  at  its  summit  the  spore-case,  or 
sporangium.    How  many  millimeters  long  is  the 
seta?    Describe  its  surface ;  its  diameter  throughout ; 
its  shape  in  imaginary  cross-section.     If  it  is  angled, 
how  many  angles  are  there?    By  taking  hold  of 
the  seta  near  its  attachment  to  the  gametophyte 
and  carefully  pulling,   separate  the  sporogonium 
from  the  gametophyte.     State,  with  full  reasons, 
whether  or  not  the  tissue  of  the  foot  appears  to  be 
continuous  with  that  of  the  gametophyte.    Does 
anything  like  grafting  of  the  sporophyte  onto  the 
gametophyte  take  place? 


76  MORPHOLOGY  AND   LIFE  HISTORY 

9.  Do  you  find  a  swelling  of  the  seta  (apophysis), 
just  beneath  the  sporangium?  If  so,  describe  and 
locate  it  accurately.  Do  its  cells  contain  chloro- 
phyll? Of  what  function  is,  or  is  not,  the  apophysis 
therefore  capable? 

10.  Remove  and  study  the  cap   (calyptra)    that  fits 
over  the  sporangium.     Describe  its  shape,  margin, 
character  of  surface,  outgrowths,  if  any. 

11.  Study  the  color,  shape,  and  other  features  of  the 
sporangium  disclosed  by  removing  the    calyptra. 
Measure    its    length    and    breadth.     Describe    its 
attitude  on  the  seta  (i.e.,  erect,  pendant,  etc).     De- 
scribe   its   outline  in  imaginary  cross-section.     If 
it  is  angled,  record  the  number  of  angles. 

12.  Describe  the  shape  and  surface  of  the  lid  (operculum) 
at  the  end  of  the  sporangium,  and  just  under  the 
calyptra. 

13.  Make  a  drawing,  ten  times  natural  size,  showing 
the  sporangium,  the  calyptra  removed,  and  a  por- 
tion of  the  seta. 

14.  Carefully  remove  the  operculum  and  preserve  it. 
On  the  margin  of  the  sporangium,  underneath  the 
operculum,  observe  the  circle  of  teeth-like  organs 
(peristome) .     Record    the    number    of    teeth.     Is 
this  number  constant?     Is  it  always  either  even 
or  odd? 

15.  In  fresh  dry  specimens  describe  the  effect  of  the 
breath  upon  the  position  of  the  teeth  of  the  peri- 
stome. 

1 6.  Describe  the  membrane   (epiphragm)   within  the 
peristome,  and  covering  the  end  of  the  capsule. 
Is  it  perforated?    What  is  its  relation  to  the  teeth 
of  the  peristome? 

17.  Make  a  drawing,  30  mm.  in  diameter,  illustrating 


POLYTRICHUM  COMMUNE  77 

an  end  view  of  the  sporangium  with  the  operculum 
removed.  Make  a  drawing  of  the  operculum, 
also  30  mm.  in  diameter. 

1 8.  With  the  razor  carefully  make  a  longitudinal  section 
of  the  capsule,  just  to  one  side  of  its  central  axis. 
Observe    the  wall  of   the   sporangium;   a  central 
organ  (columella) ;  and,  between  the  two,  a  mass 
of  spores. 

19.  Describe  the  structural  relation  of  the  columella 
to  the  epiphragm.     What,  in  reality,  is  the  latter? 

20.  Describe  the  relative  number,  color  and  attach- 
ment or  non-attachment  of  the  spores,  so  far  as 
may  be  ascertained  without  the  aid  of  the  micro- 
scope. 

21.  Make  a  drawing,  ten  times  natural  size,  illustrating 
everything  observed  under  18-20. 

22.  From  the  above  observations  construct  a  diagram  of 
an  imaginary  cross-section  of  the  sporangium  near 
the  middle.     Compare  the  diagram  with  an  actual 
cross-section. 

23.  Carefully  preserve   the  sporophyte  in  a  covered 
watch-glass  or  other  convenient  moist  (not  wet) 
place  until  the  next  laboratory  period,  or  proceed  at 
once  with  the  following  observations  (D) : 

D.  Microscopic  Characters: 

THE  SPOROPHYTE 

1.  With  a  sharp  scalpel  remove  a  thin  piece  from  the 
base  of  the  sporangium,  cutting  parallel  to  the  sur- 
face, and  mount  it  in  water  with  the  outer  surface 
uppermost. 

2.  Examine  the  mounted  tissue  under  the  low,  then 
under  the  high  power,  to  see  if  stomata  are  present. 
If  they  are,  describe  them  and  their  distribution. 


7  8  MORPHOLOGY  AND   LIFE   HISTORY 

Compare  them  with  the  stomata  of  a  foliage-leaf 
of  one  of  the  higher  plants,  including  the  number, 
shape,  and  other  characters  of  the  guard-cells.  In 
like  manner  compare  them  with  the  stomata  of  the 
fern.  State,  with  reasons,  which  type  of  stomata 
you  consider  the  more  primitive.  Look  for  stomata 
on  the  surface  of  the  apophysis. 

3.  Study  thin  cross-sections  of  the  sporangium  (sec- 
tions of  the  half  (C,  18)  will  serve).     Identify  the 
parts    already   studied,   and  their  characters  and 
relationship  as  seen  in  cross-section.     Make  your 
drawings  at  least  20  mm.  in  radius. 

4.  Describe  the  shape  of  the  spores,  and  their  manner 
of  attachment  or  non-attachment,  as  seen  under 
high  power.     Of  how  many  cells  is  one  spore  com- 
posed?    Make  a  drawing  of  three  spores  making 
each  10  mm.  in  longest  measure. 

5.  Mount  thin  cross-sections  of  the  seta,  and  study 
under  high  power. 

6.  Distinguish    the    outer    layer,    epidermis.    How 
many  cells  thick  is  it?    Observe  the  central  strand, 
and  between  this  and  the  epidermis  a  thin-walled 
tissue  (parenchyma),  and  a  layer  of  thicker  walled 
cells    (sclerenchyma).    State   how    these   various 
tissues  may  be  distinguished  from  each  other.     Of 
what    value    is    the    sclerenchyma?     The    central 
strand  is  comparable  with  the  nbro-vascular  bundle 
of  the  seed-bearing  plants.     Draw. 

THE  GAMETOPHYTE 
The  Leaf. 

7.  Remove  an  entire  leaf  and  mount  it  in  water.     Ob- 
serve under  low,  then  under  high  power. 

8.  How  many  cells  thick  is  it.    Is  it  of  uniform  thick- 


POLYTRICHUM   COMMUNE  79 

ness?  Describe.  Are  stomata  present?  Why? 
How  is  the  midrib  distinguished?  Describe  the 
leaf-margin  and  apex.  Describe  any  differences 
in  the  two  sides  of  the  leaf. 

9.  Describe  fully  the  contents  of  a  single  cell,   as 
observed  under  high  power. 

10.  Illustrate  by  suitable  drawings  all  features  observed 
under  D,  7-9. 

The  Stem. 

11.  Study,  under  the  low  power,  cross-sections  of  the 
stem  mounted  in  clearing  fluid  (or  use  prepared 
slides) . 

12.  Describe  the  tissues  observed,  and  their  relation  to 
each  other.     Compare  the  structure  of  the  game- 
tophyte-stem,  as  seen  in  cross-section,  with  that  of 
the  sporophyte-stem,  and  name  the  tissues  of  the 
former,  using  the  terms  given  above  (Z>,  6). 

13.  Illustrate  by  a  drawing,  at  least  50  mm.  in  diameter, 
the  structure  of  the  stem  as  seen  in  cross-section. 

E.  Non-sexual  Reproduction: 

1.  In  some  mosses  a  second  gametophyte  often  devel- 
ops from  the  tip  of  an  older  plant.     This  is  called 
proliferation.     Frequently  this  may  be  repeated  a 
number  of  times,  forming  a  chain  of  plants,  each 
younger  one  growing  out  of  the  apex  of  the  next 
older  one.    Examine  the  material  at  hand,  and,  if 
such  a  condition  is  found,  describe  it,  with  drawing. 
What  kind  of  reproduction  is  this? 

2.  Explain  the  advantage  to  the  species  of  the  elon- 
gation of  the  seta. 

3.  If  stages  in  the  germination  of  the  spores  are  avail- 
able,  study   this  process.     The   structure   imme- 
diately developed  from  the  spore  is  the  protonema. 


80  ^  MORPHOLOGY  AND   LIFE   HISTORY 

Describe  its  color.  Is  it  simple  or  branched?  Are 
cross-walls  present? 

4.  At  certain  points  on  the  protonema  observe  buds. 
These  buds  develop  into  either  male  or  female  game- 
tophy tes  (gametophores) . 

5.  Which  generation  of  the  moss-plant  always  devel- 
ops from  the  spore?     Compare  this  with  the  case  in 
the  fern. 

F.  Sexual  Reproduction: 

The  antheridia 

1.  Take  a  male  gametophyte  and,  with  a  dissecting 
needle,  carefully  remove  some  of  the  antheridia, 
borne  in  the  rosette  at  the  summit  of  the  plant. 
Mount  them  in  water,  and  study  them  under  the 
microscope. 

2.  Describe  the  shape  and  other  structural  features 
of  the  antheridia.     What  is  their  color?     Compare 
them  with  the  antheridia  of  the  fern. 

Do  you  find  paraphyses  associated  with  the  anther- 
idia? If  so,  describe  them,  and  state  how  they 
may  be  distinguished  from  the  antheridia. 

4.  If  prepared  slides  are  available,  study  longitudinal 
sections  through  the  tip  of  the  male  gametophyte, 
observing  the  mode  of  attachment  of  the  antheridia. 

5.  With  high  power  study  the  sperms  (spermatozoids) 
within  the  antheridia. 

6.  In  fresh  specimens  the  sperms  may  be  seen  swim- 
ming about  in  the  water.     If  motile  sperms  are 
present,  endeavor  to  make  out  the  number  and 
character  of  their  organs  of  locomotion  (cilia).     Do 
the  cilia  precede  or  follow  as  the  sperm  moves  for- 
ward?    Do  the  motions  of  the  sperm  appear  to  be 
purposeful  or  not?     Give  reasons  for  your  answer. 


POLYTRICHUM  COMMUNE  8 1 

7.  Make  drawings  showing  all  features  observed  under 
F,  1-6.     The  antheridia  should  be  at  least  25  mm. 
long;  the  body  of  the  sperms  10  mm.  long. 

The  archegonia 

8.  With   the  female   gametophyte   make   studies   as 
directed  above  (F,  1-4). 

9.  In  the  archegonium  distinguish  the  venter,  neck, 
and  lid-cells.     Is  the  archegonium  sessile  or  stalked  ? 

10.  If    prepared    slides    are    available,    identify    the 
oosphere,  or  egg,  and  the  neck-canal.    How  many 
cells  thick  is  the  wall  of  the  archegonium?     Is  this 
uniform? 

11.  Make  a  drawing,  at  least  35  mm.  long,  showing  all 
features  observed  under  F,  8-10. 

12.  Describe  the  conditions,  processes,  and  organs  in- 
volved in  sexual  reproduction  in  the  moss.     Explain 
whether  or  not  it  is  of  advantage  to  the  moss-plants 
that  they  grow  so  close  together. 

13.  Into  what  does  the  fertilized  egg  develop?    Where 
does  it  develop? 

G.  Nutrition  and  Growth:1 

The  gametophyte 

1.  Is  the  gametophyte  of  the  moss  capable  of  elabor- 
ating its  own  carbohydrate  food?    Explain.    Is  it 
dependent  upon  the  sporophyte  at  any  period  of  its 
existence?     Explain. 

2.  How  does  the  possession  of  leaves  affect  the  surface- 
area  of  the  chlorophyll-bearing  tissues?     Explain 
how  this  affects  the  process  of  photosynthesis. 

1  This  may  be  assigned  for  home  work  and  serve  as  the  basis  of  class 
discussion,  or  of  written  work  to  be  handed  in. 
6 


82  MORPHOLOGY  AND   LIFE   HISTORY 

3.  State  the  organs  and  processes  by  which  water  and 
inorganic  salts  are  taken  in  by  the  gametophyte. 

4.  Explain  the  presence  or  absence  of  stomata  in  this 
plant. 

5.  By  what  organs  is  the  respiration  of  the  game  to- 
phyte  carried  on? 

6.  Does  the  gametophyte  have  to  elaborate  food  in  ex- 
cess of  its  own  needs?    Explain.     Explain  the  need 
or  lack  of  need  of  conducting  tissues  in  the  gameto- 
phyte. 

7.  Name  two  ways  in  which  the  gametophyte  is  kept 
rigid  and  erect. 

The  sporophyte 

8.  Can  the  sporophyte  lead  an  independent  existence 
at  any  time  in  its  history?    Explain. 

9.  By  what  organ  or  organs,  by  what  process,  and  from 
what  source  are  water  and  dissolved  food  substances 
taken  into  the  sporophyte? 

10.  Is  photosynthesis  possible  in  the  sporophyte  at  any 
period  of  its  existence?    What  is  the  source  of  its 
carbohydrate  food? 

11.  Explain  the  need  or  lack  of  need  of  conducting  tis- 
sues in  the  sporophyte.     Compare  the  degree  of 
development  of  these  tissues  in  the  sporophyte  and 
gametophyte  of  the  moss. 

12.  Explain  the  significance  of  the  presence  or  absence 
of  stomata  in  the  sporophyte. 

13.  Refer  to  the  question  in  F,  13,  and  explain  the  origin 
of  the  calyptra.    To  which  generation  does  it  be- 
long?   Explain. 

14.  Explain  the  advantage  of  sclerenchymatous  tissue 
in  the  sporophyte.     Describe  the  distribution  of 


POLYTRICHUM   COMMUNE  83 

this  tissue  in  the  seta,  and  explain  whether  or  not 
this  is  an  added  advantage. 

15.  After  the  sporophyte  of  Polytrichum  begins  to  de- 
velop, does  it  grow  continuously  until  maturity,  or 
does  a  period  of  prolonged  rest  intervene?    Is  the 
same  true  with  the  sporophyte  of  the  fern? 

16.  As  directed  in  7,  10,  p.  72,  diagram  the  life  history 
of  the  moss. 

17.  Outline  the  life  history  of  the  moss,  as  described  in 
7,  n,  p.  72. 

H.  Comparisons: 

1.  Write  the  following  names  of  organs  of  the  gameto- 
phyte  of  the  moss- in  a  column,  and  opposite  them, 
in  another  column,  the  names  of  the  corresponding 
organs  of  the  fern;  thallus,  rhizoid,  antheridiophore, 
archegoniophore,  antheridia,  sperm,  archegonium, 
egg,  paraphyses. 

2.  In  a  similar  manner  compare  the  organs  of  the  sporo- 
phytes  of  the  two  plants,  adding  the  names;  sto- 
mata,  foot,  calyptra,  columella,  apophysis,  sporan- 
gium. 

3.  In  a  third  column  make  a  list  of  organs  of  the  moss 
not  found  in  the  fern;  in  a  fourth  column,  the  organs 
of  a  fern  not  found  in  the  moss. 

4.  Compare  the  degree  of  organization  of  the  gameto- 
phytes  of  the  fern  and  the  moss,  as  illustrated  by 
Poly  podium  and  Polytrichum. 

5.  In  like  manner  compare  the  sporophytes  of  the  two 
classes  of  plants. 

6.  State  several  reasons  for  regarding  Polytrichum  as 
either  more  or  less  highly  organized  than  Poly- 
podium. 


Marchantia  polymorpha  (A  LIVERWORT) 

A.  Classification: 

Division  II.     Bryophyta  (moss-plants). 
Class  I.     Hepaticae  (liverworts). 
Order.     Marchantiales  (marchantia-f orms) . 
Family.     Marchantiaceae. 
Genus.     Marchantia. 
Species,    polymorpha. 

THE  GAMETOPHYTE 

B.  Habitat: 

i.  This  plant  grows  very  abundantly  on  the  soil  of 
flower  pots  and  benches  in  nearly  all  greenhouses. 
In  places  it  becomes  a  great  annoyance  to  gardeners, 
and  is  very  difficult  to  get  rid  of.  Out  of  doors  it 
grows  in  moist,  shady  places,  frequently  on  rocky 
ledges  by  streams. 

C.  Naked-eye  Characters: 

1.  Examine  first  a  non-" fruiting"  specimen. 

2.  Is  the  plant-body  a  thallus?     Describe  its  color, 
outline,  and  manner  of  branching.     What  term  is 
applied  to  this  manner  of  branching?     Does  the 
plant  possess  dorso-vertral  differentiation?    If  so, 
how   are   the   dorsal  and  ventral  surfaces  distin- 
guished? 

3.  Note  the  texture  of  the  plant,  to  be  ascertained  by 
carefully  breaking  off  a  piece  of  fresh  thallus. 

4.  Describe  the  appearance  of  the  dorsal  surface.     The 

84 


MARCHANTIA  POLYMORPHA  85 

small  areas  into  which  it  is  marked  off  are  areolae. 
In  the  center  of  each  areola  find  evidence  of  a 
stoma.  Is  there  a  midrib? 

5.  The  cup-shaped  structures  on  the  dorsal  surface 
are   called  cupules.     Do   they   occur   on   definite 
portions  of  the  thallus  (i.e.,  margin,  midrib,  etc.), 
or  irregularly?     Describe  their  color,  shape,  height, 
diameter,  margin.     Are  they  sessile  or  stalked? 

6.  The  non-sexual   (vegetative)   reproductive  bodies 
within   the   cupules   are   brood-buds,   or  gemmae 
(sing.,  gemma).    Describe  the  color,   shape  and 
size  of  one  (use  hand  lens).     How  are  they  attached 
to  the  plant?     Do  all  the  cupules  contain  them? 
Explain  your  observation  on  this  point. 

7.  Examine  the  ventral  surface  of  the  plant.     De- 
scribe its  color  and  surface  markings,  and  compare  in 
these  respects  with  the  dorsal  surface. 

8.  Note  the  root-like  filaments  or  rhizoids.     Describe 
their   shape,    color,   dimensions,    and   distribution 
over  the  ventral  surface. 

9.  Find  purple,  leaf-like  structures  (scales)  among  the 
rhizoids,   and  describe  their  form,  position,   and 
distribution. 

10.  Make  careful  drawings,  showing: 

(a)  The  plant-body,  natural  size. 

(b)  The  surface  markings  of  the  dorsal  surface, 
enlarged  ten  times. 

(c)  A  cupule,  side  view  in  perspective,  enlarged 
ten  times. 

(d)  An  outline  of  a  gemma  enlarged  ten  times. 

11.  Make  a  diagram  of  an  imaginary  cross-section  of 
the  plant-body,  passing  through  one  or  more  cupules 
(ten  times  natural  size).    Label  all  parts  of  the 
drawings. 


86  MORPHOLOGY  AND   LIFE   HISTORY 

D.  Microscopic  Characters: 

1.  The  rhizoids. 

(a)  With  the  forceps  carefully  remove  a  few  of  the 
rhizoids  and  mount  them  in   clearing  fluid. 
Examine  them  first  under  low,  then  under  high 
power. 

(b)  Do  you  find  different  kinds  of  rhizoids?    If  so, 
how  are  they  distinguished?    Are  there  cross- 
walls?    Describe  the  contents  of  the  rhizoidis 
Do  they  branch?    Explain  the  shape  of  their 
tips,  and  the  thickness  of  their  cell-walls. 

2.  The  gemmae. 

(a)  Remove  several  gemmae  with  a  scalpel,  being 
careful  not  to  cut  or  otherwise  injure  them, 
and  mount  them  in  a  drop  of  water.    Examine 
with  low  power. 

(b)  Are  the  gemmae  more  than  one  cell  thick?    Is 
their  thickness  uniform?    Describe. 

(c)  Find  on  the  margin  the  scar,  where  the  gemma 
was  attached  to  its  pedicle,  or  stalk. 

(d)  Find  two  vegetative  notches,  180°  apart.    How 
do  they  differ  from  the  scar?    Find  papilla-like 
cells  in  these  notches.    Do  they  contain  chloro- 
phyll?   Do    they   secrete   mucilage?    In   the 
apex  of  each  of  these  notches  is  a  vegetative 
point  from  which  a  new  thallus  will  develop. 
Mucilage  protects  it. 

(e)  Are  there  any  surface  outgrowths?    Is  there 
dorso-ventral  differentiation?     Compare  them 
in  this  respect  with  the  thallus  to  which  they 
give  rise.    So  far  as  you  can  detect,  would  it 
make  any  difference  which  side  up  the  gemma 
lay  when  it  was  sown? 


MARCHANTIA  POLYMORPHA  87 

(/)   In  the  cells  of  a  gemma  do  you  find  chloroplasts? 

Nucleus  ?    Oil  drops? 
(g)  Note  the  larger  cells  with  clear  contents  from 

which  the  rhizoids  will  develop.    Do  they  con- 
tain chlorophyll? 
(ti)  Make  a  drawing  50  mm.  in  diameter,  showing 

all  the  features  observed  under  D,  2. 
(i)   Draw  the  outline  of  an  imaginary  cross-section 

passing  through  the  center  of  a  gemma. 
The  thallus. 
(a)  Under  high  power  study  the  surface  cells  and 

stomata.    How  many  guard-cells  are  there? 

Compare  the  stomata  of  Marchantia  with  those 

of  a  foliage-leaf  of  a  higher  plant,  and  of  the 

moss  and  fern. 
(6)  Study  cross-sections  of  the  plant  mounted  in 

clearing  fluid. 

(c)  The  careful  study  of  the  structure  of  the  foliage- 
leaf,    already    made,    makes    it    unnecessary 
to  give  detailed  directions  for  these  observa- 
tions.   Frame    your    own    questions,    to    be 
answered  by  observing  the  mounted  section. 
Note  especially  whether  the  tissues  are  differ- 
entiated, and,  if  so,  compare  with  a  foliage-leaf 
in  this  respect. 

(d)  Look  for  sections  passing   through  stomata, 
and  compare  their  structure  with  that  of  the 
stomata  of  the  leaf.    What  causes  the  surface 
appearance  of  the  margins  that  delimit  the 
areolae? 

(e)  Describe  the  place  and  mode  of  origin  of  the 
rhizoids;  of  the  cupules. 

(f)  Is  the  thallus  of  the  same  thickness  throughout? 

(g)  Describe   the   chloroplasts.    In   some   of   the 


88  MORPHOLOGY  AND   LIFE   HISTORY 

cells  brown  oil  globules  may  be  observed. 
If  these  are  found,  describe  their  location, 
and  relative  size.  Do  the  cells  that  contain 
oil  globules  also  contain  protoplasm?  Infer 
the  source  of  the  oil. 

(ti)  Make  drawings  to  illustrate  all  features  observed 
under  Z>,  3. 

E.  Vegetative  Propagation: 

1.  There   are   two   ways   in   which   Marchantia   can 
propagate  itself  without  the  intervention  of  gametes. 
In  the  first  place,  a  portion  of  the  thallus  broken 
off  is  capable  of  developing  into  a  mature  individual. 
Somewhat,  though  not  sharply,  distinguished  from 
this    method   is    reproduction   by   means    of    the 
gemmae.     State  two  differences  between  a  gemma 
and  a  fern  or  moss  spore. 

2.  Incorporate  the  above  facts  into  your  notes  at  this 
point,  using  your  own  language,  and  state  to  what 
kind  of  reproduction  each  of  the  above  methods 
belongs. 

F.  Sexual  Reproduction: 

i.  Study  plants  having  the  upright  stalks  which  bear 
the  sexual  reproductive  organs. 

The  antheridial  branch 

Naked-eye  Characters: 

(a)  The  stalks  having  the  mushroom-shaped  tops 
bear  the  antheridia,  and  are  hence  called  the 
antheridial  branches,  or  antheridiophores.    The 
expanded  portion  borne  at  the  summit  of  the 
stalk,  is  the  antheridial  receptacle. 

(b)  Study  and  describe  the  stalks  of  the  antheridio- 
phores.   On  what  region  of  the  thallus  are  these 


MARCHANTIA  POLYMORPHA  89 

structures  borne?  On  which  surface  do  they 
originate?  State  their  average  height  in  milli- 
meters. Describe  the  grooves  on  the  surface. 
How  many  are  there? 

(c)  Describe  the  color  of  the  stalk.     Are  stomata 
present  ?     Epidermal  hairs  or  other  outgrowths  ? 
If  so,  describe. 

(d)  Do  you  find  any  antheridiophores  that  branch? 

(e)  Describe  carefully  the  appearance  of  the  upper 
surface    of   the  antheridial  receptacle,   noting 
the  occurrence  and  distribution  of  any  struc- 
tures or  surface  marks. 

(/)    Is  this  surface  perfectly  plane?     If  not,  describe. 

(g)  Make  drawings,   twice  natural  size,   showing 
all  points  observed  under  F,  i,  (a)-(f),  including 
a  cross-sectional  view  of  the  stalk. 
Microscopic  Characters: 

(ti)  Study  and  describe  with  drawings  .(5  cm. 
in  diameter),  the  structure  of  the  stalk  of 
an  antheridiophore  as  seen  in  cross-section. 

(i)  Using  prepared  slides,  study  thin  longitudinal 
sections  passing  through  a  receptacle  and 
portion  of  the  stalk.  Is  there  a  differentiation 
into  epidermis  and  other  tissues?  Describe 
in  detail.  Note  the  intercellular  air-spaces. 
In  what  part  of  the  structure  do  they  occur? 
Suggest  any  advantage  these  air-spaces  may  be 
to  the  plant. 

(k)  Observe  the  chambers  opening  at  the  surface 
through  necks,  and  containing  the  antheridia. 
How  many  antheridia  in  each  chamber?  De- 
scribe their  shape,  and  mode  of  attachment. 
How  many  cells  thick  is  the  wall  of  the  anther- 
idium?  Do  the  wall-cells  contain  chlorophyll? 


QO  MORPHOLOGY  AND   LIFE   HISTORY 

(/)  Describe  variations  in  the  size  of  the  antheridia, 
and  explain.  Locate  them  according  to  size. 

(m)  Do  you  find  papillae  (paraphyses)  at  the  base 
of  the  antheridia?  If  so,  of  how  many  cells  are 
they  composed?  Describe  their  shape  and 
appearance. 

(n)  Describe  the  appearance  of  the  contents  of  an 
antheridium.  In  the  mature  antheridium  the 
contents  are  mature  antherozoids  or  sperms. 
Younger  antheridia  contain  sperm-mother- 
cells.  Describe  their  appearance  accurately. 

(0)  Illustrate  by  suitable  drawings  all  the  features 
observed  under  F,  i,  (i)-(n). 

The  archegonial  branch 

Naked-eye  Characters: 

(p)  The  stalks  having  the  umbrella-shaped  tops 
bear  the  female  reproductive  organs  or  arche- 
gonia,  and  are  called  archegoniophores.  The 
expanded  portion  at  the  top  of  the  stalk  is  the 
archegonial  receptacle. 

(q)  Do  the  archegonial  and  antheridial  branches 
occur  on  the  same  plants?  Measure  the  height 
of  the  stalks  of  several  mature  archegoniophores, 
and  compare  their  average  height  with  the  aver- 
age height  of  the  stalk  of  the  mature  antheridio- 
phore.  Is  the  stalk  of  the  archegoniophore 
grooved? 

(r)  Describe  the  markings  of  the  upper  surface  of 
the  receptacle,  and  compare  it  with  the  dorsal 
surface  of  the  thallus.  Are  stomata  present? 
Record  the  number  of  rays  on  your  specimen. 
Compare  several  specimens  on  this  point. 


MARCHANTIA  POLYMORPHA  9 1 

(5)   Describe  the  under  surface.    Note  the  fringed 

membranes,  (perichaetium). 
Microscopic  Characters: 

(0  Study  and  describe,  with  drawings  (5  cm.  in 
diameter),  the  structure  of  the  stalk  of  an 
archegoniophore  as  seen  in  cross-section.  Com- 
pare this  with  the  antheridiophore  (F,  (ti),  p. 

89). 

(u)  Using  prepared  slides,  study  longitudinal  sec- 
tions of  the  receptacle  passing  through  one  of 
its  arms.  If  fresh  or  preserved  material  is  at 
hand  in  sufficient  quantity,  the  study  may  be 
made  from  material  " teased  out"  on  the 
slide. 

(v)  Study  the  tissues  of  the  receptacle.  Is  there  an 
epidermis?  Stomata?  Describe  (a)  the  tis- 
sues just  beneath  the  surface  layer  of  cells; 
(b)  those  more  deeply  seated. 

(w)  Observe  the  flask-shaped  archegonia  hang- 
ing from  the  lower  surface  of  the  receptacle. 
Can  you  distinguish  two  regions — venter  and 
neck.  Note  the  passage,  or  neck-canal,  leading 
from  the  venter  through  the  neck,  and  opening 
at  the  summit.  How  many  cells  thick  is  the 
wall  of  the  archegonium?  Compare  with  the 
archegonia  of  mosses  and  ferns. 

(x)  Surrounding  a  mature  archegonium  observe  the 
section  of  a  cup-like  structure,  the  perigynium. 

(y)  Within  the  venter  of  an  archegonium  just 
matured  observe  a  single-celled  ovum,  or  egg. 

(z)  Make  drawings  illustrating  all  features  shown 
under  (u)  —  (y),  and  preserve  the  mounted 
section  for  subsequent  study. 


Q2  MORPHOLOGY  AND   LIFE   HISTORY 

G.  Physiology: 

1.  Is  photosynthesis  possible  with  the  thallus?     The 
antheridiophore?     The    archegoniophore?     What 
correlation   do    you   find   between   structure   and 
function  in  this  respect  in  the  archegoniophore? 

2.  Explain  the  nutrition  of  the  non-chlorophyll-bear- 
ing cells  of  the  gemmae.     What  is  their  nutritive 
relation  to  the  gemma  as  a  whole? 

3.  Is  the  gametophyte  capable  of  an  independent  ex- 
istence?    Thoughtfully  consider  and  then  describe 
the  correlation  between  structure  and  function  in 
this  respect. 

4.  In  mature  specimens  grayish  drops  of  liquid  may 
often  be  found  exuding  on  the  dorsal  surface  of  the 
antheridiophores.     This  liquid  contains  active  an- 
therizoids,  or  sperms.     Mount  some  of  it  in  water, 
and,  under  high  power,  observe  the  motion,  organs  of 
motion,  and  other  structural  features  of  these  sperms. 

5.  When  longitudinal  sections  of  mature  archegonia 
are  mounted  in  water  containing  active  sperms  the 
behavior  of  the  latter  toward  the  former  may  be 
readily   observed.     If   your   material   is    suitable, 
make  these  studies. 

6.  How  only  can  the  sperms  reach  the  egg?    What 
external  conditions  would  be  favorable  for  this? 

7.  Of  what  advantage  is  it  to  the  sporophyte  to  have 
the  egg  retained  in  the  venter  of  the  archegonium? 
Would  this  be  of  as  great  advantage  in  any  aquatic 
plant,  as  in  a  land  plant?    Why? 

8.  Is  the  small  size  of  the  sperms  of  any  special  advan- 
tage to  the  plant?     Explain. 

9.  Explain  any  advantage  in  the  greater  height  of  the 
mature  archegoniophore  over  that  of  the  antheridio- 
phore. 


MARCHANTIA  POLYMORPHA  93 

10.  Enumerate  several  facts  that  insure  a  wide  distribu- 
tion of  Marchantia. 

THE  SPOROPHYTE 

A .  Origin  of  the  Sporophyte: 

i.  What  is  the  process  of  the  fusion  of  the  egg  and 
sperm  called?  What  is  the  body  that  results 
from  this  fusion  called?  This  body,  by  successive 
cell-division,  develops  into  the  sporogonium  or 
sporophyte. 

B.  Naked-eye  Characters: 

1.  In  a  mature    specimen    observe    the   small  bell- 
shaped   organs    (sporangia)    pendant   on   a   stalk 
between  the  perichsetia.     The  sporangia  and  stalk 
together  form  the  sporogonium,  or  sporophyte  stage 
of    Marchantia.     In   fresh    mature    specimens  an 
orange-colored  mass  containing  spores  is  easily  seen 
at  the  end  of  the  sporophyte.    Are  the  sporogonia 
borne  on  a  line  with  the  rays  or  between  the  rays? 

2.  Make  drawings,  four  times  natural  size,  showing  the 
archegoniophore  as  seen  from  (a)  the  top;  (6)  the 
side;  (c)  the  underside. 

3.  After  making  the  drawings,  as  directed  in  B,  2, 
carefully  dissect  out  one  mature  sporogonium  and 
place  it  in  a  watch-glass  to  examine.     Make  a 
drawing  50  mm.  long,  showing  all  features  observed, 
labeling  the  foot,  stalk,  and  sporangium.    Write  a 
brief  but  clear  description  of  the  sporogonium. 

C.  Microscopic  Characters: 

i.  If  prepared  slides  are  available  of  sections  passing 
through  the  archegonia  (F  (w)  above),  find  various 
stages  in  the  development  of  the  sporophyte  within 
the  archegonium.  In  nearly  mature  specimens 


94  MORPHOLOGY  AND   LIFE   HISTORY 

observe  the  attachment  of  the  sporophyte  to  the 
receptacle  by  means  of  the  foot.  This  study  may  be 
made  to  advantage  with  fresh  or  preserved  material 
teased  out  on  the  slide.  In  such  preparations  there 
will  be  observed,  surrounding  the  sporogonium,  the 
membrane  formed  by  the  growth  of  the  perigynium. 
2.  In  the  mount  already  made  (or  in  a  fresh  mount  of 
the  orange-colored  mass  referred  to  in  (B,  i,  p.  93), 
observe  the  spore-mother-cells  (sporocytes)  or,  in 
older  specimens,  the  spores  (in  strands  or  separate, 
depending  on  the  stage  of  development),  and  the 
elongate  elaters.  What  is  the  size  of  the  spores,  and 
the  number  of  cells  of  which  they  are  composed? 
Describe  their  shape,  and  any  surface  marks  ob- 
served. Describe  any  marks  on  the  elaters.  Of 
how  many  cells  is  an  elater  composed?  Mount,  dry, 
some  of  the  mass  that  contains  elaters,  and  observe, 
under  the  low  power,  their  behavior  as  water  is 
added. 

3.  Are    the    antheridiophores    and    archegoniophores 
sexual  organs?    Why?    What  are  the  sexual  organs 
of  Marchantia? 

4.  Name  and  classify  (sexual  or  asexual)  four  different 
kinds  of  reproductive  bodies  produced  by  this  plant. 
Consider  carefully  whether  the  spores,  produced 
by  the  sporophyte,  are  sexual  or  asexual  reproduc- 
tive bodies. 

D.  Physiology: 

1.  Can  photosynthesis  take  place  in  the  sporophyte? 
Explain  your  answer. 

2.  From  what  source,  by  what  organ  or  organs,  and 
by  what  physical  process  does  the  sporophyte  ob- 
tain its  water  and  dissolved  food?     Compare  it 
with  the  gametophyte  in  this  respect. 


MARCHANTIA  POLYMORPHA 


95 


E.  Comparison  of  Gametophyte  and  Sporophyte: 

1.  Compare  the  degree  of  development  or  organiza- 
tion of  sporophyte  and  gametophyte. 

2.  Copy  the  following  table  into  your  laboratory  note- 
book and  mark  x  after  the  word  gametophyte  or 
sporophyte  in  the  proper  column. 

TABLE  II 


8 

i  o 

5 

1 

1 

**% 

« 

a 

.2$ 

8 

| 

*'t 

•§> 

Generation 

1 

1 

o 

1 

*o  « 

P, 

rt 

a 

8 

1 

||| 

II 

1 

§ 

Jl 

I 

I 

1 

ill 

0 

3.  State  reasons  why  you  consider  Marchantia  higher 
or  lower  than  (a)  the  moss;  (b)  the  fern. 

4.  Diagram  the  life  cycle  of  Marchantia,  as  directed 
for  the  fern  (/,  n,  p.  72). 

5.  Indicate  the  life  history  of  Marchantia  for  three  gen- 
erations, as  directed  in  /,  10,  p.  72. 

6.  Does  the  gametophyte  ever  produce  another  game- 
tophyte directly?     Does  the  sporophyte  ever  pro- 
duce another  sporophyte  directly?     If  so,  explain 
how.    What  phase  intervenes  between  two  gameto- 
phytes  in  the  alternation  of  generations?     Between 
two  sporophytes?    Is  this  always  the  case  so  far 
as  your  own  studies  show?     Explain  what  is  meant 
by  the  expression,  "alternation  of  generations." 


Fucus  vesiculosus  (BLADDER  WRACK) 

A.  Classification: 
Division  I.     Thallophyta. 

Subdivision  I.     Algae. 

Class  III.     Phaeophyceae  (brown  algae). 
Order.     Fucales. 
Family.     Fucaceae. 
Genus.    Fucus. 
Species,     vesiculosus. 

B.  Habitat: 

i.  Ascertain  the  habitat  of  this  plant  from  your  read- 
ing and  class  discussions,  and  record  it  in  your 
laboratory  notes  at  this  place. 

C.  Naked-eye  Characters: 

1.  These  characters  may  be  best  studied  by  floating  a 
fresh  specimen  in  a  dish  of  sea-water.     Material 
preserved  in  formalin  should  be  rinsed  under  the 
tap,  and  then  floated  in  fresh  water. 

2.  Describe  the  color,  shape,  and  size  of  the  thallus. 
Does  it  form  lateral  branches  or  approximately 
equal  terminal  branches  (dichotomy,  forking). 

3.  Do  you  find  any  holdfasts,  or  organs  of  fixation? 
If  so,  describe  them.     State  reasons  why  you  think 
they  are  true  roots  or  not. 

4.  Is  there  a  midrib?    A  stalk,  or  stipe?    Do  you 
consider  that  the  plant  is  differentiated  into  root, 
stem,  and  leaf?     Give  reasons. 

5.  Describe  the  distribution  of  bladders.    Why  is  this 
species  called  "vesiculosus"? 

96 


FUCUS  VESICULOSUS  97 

6.  Observe  the  swollen  tips,  receptacles.     Do  the  tips 
of  all  the  branches  bear  receptacles?     How  may 
they  be  distinguished  from  the  bladders? 

7.  Carefully  note  the  dot-like  projections  on  the  re- 
ceptacles.    Find  the  circular  openings  in  these  pro- 
jections, the  ostioles. 

8.  Do  you  find  ostioles  elsewhere  than  on  the  recep- 
tacles?    If  so,  describe  their  distribution  over  the 
surface  of  the  thallus.     Where  are  they  not  found? 

9.  Observe    carefully    the    emarginate    tips    of    the 
branches  that  do  not  bear  receptacles.     Do  you 
find  a  groove  in  these  tips?     If  so,  is  it  in  the  plane 
of  the  thallus,  or  not? 

10.  Make  careful  drawings,  natural  size,  showing  all 

points  noted  under  C. 
D.  Microscopic  Characters: 

i.  Mount  in  water  thin  cross-sections  taken  through 
the  thin  expanded  portion  of  the  thallus,  and  study 
under  the  low  power. 

Note  the  differentiation  of  the  tissue  into  central 
tissue  or  medulla,  and  a  cortical  tissue.  How  are 
the  two  distinguished? 

3.  Observe  that  the  outer  layer  of  cells  of  the  cortical 
tissue  is  further  differentiated  into  an  epidermoidal 
tissue.     Describe  it.     This  outer  layer  is  not  a  true 
epidermis,  like  the  outer  layer  of  cells  of  the  leaf. 
In  the  younger  portions  of  the  thallus  its  cells,  by 
division,  give  rise  to  the  cells  which  form  the  under- 
lying  tissues.     None   of  the   alga  possess   a   true 
epidermis. 

4.  Is   starch  present  in   the   cortical   tissue?     Chlo- 
rophyll?   Note  the  layer  of  cuticle  on  the  outer 
cell-walls  of  the  epidermoidal  layer. 

<.  Note  that  the  cells  in  the  medulla  tend  to  form  a 


98  MORPHOLOGY  AND   LIFE   HISTORY 

thread-like  network.  Does  starch  occur  in  this 
tissue?  Some  of  the  cells  unite,  end  to  end,  form- 
ing tubes  to  conduct  liquids. 

6.  Between  the  cells  of  both  cortex  and  medulla  is  a 
mucilaginous  layer,  formed  by  the  swelling  and 
chemical   transformation   of   the  middle  lamella, 
or  layer  that  separates  adjacent  cell-walls. 

7.  Make  a  drawing   showing  the  differentiation  of 
tissues  from  the  surface  to  the  center  of  the  thallus. 

8.  Sterile  Conceptacles:  Secure  sections  passing  through 
one  or  more  of  the  ostioles  that  do  not  occur  on  the 
receptacles.     These  ostioles  will  be  found  to  open 
into  spherical  or  pear-shaped  cavities  (conceptacles) 
imbedded  in  the  cortical  tissue.     In  viewing  a  cut 
end  of  the  thallus  with  the  naked  eye,  these  cavities 
appear  as  minute  dots  underneath  the  epidermoidal 
layer. 

9.  Observe  in  these  conceptacles,  under  the  low  power, 
numerous  long  hairs  (paraphyses).     Of  how  many 
cells  is  each  composed?     Do  they  extend  through 
the  ostioles  to  the  surface?    With  what  are  they 
connected? 

E.  Physiology: 

1.  Of  what  advantage  to  an  aquatic  plant  may  the 
air-containing  bladders  be? 

2.  Does  the  plant  grow  attached  to  a  substratum? 
If  so,  how? 

3.  How  do  you  think  the  plant  takes  in  its  food  ele- 
ments? 

4.  Ascertain  if  the  plant  has  chlorophyll.     Is  photo- 
synthesis possible? 

5.  Would  it  be  an  advantage  to  this  plant  to  have  a 
system  for  conducting  liquid  nutrients  from  one 
place    to    another?     Is    such    a    system   present? 


FUCUS  VESICULOSUS  99 

In  attempting  to  answer  this  last  question  recall 
the  habitat  of  Fucus. 

F.  Vegetative  Propagation: 

1.  Vegetative  propagation  is   accomplished    by    the 
breaking  off  of  branches  which  may  float  away 
and  become  established  as  new  individuals. 

2.  Frequently,  by  a  process  of  regeneration,  dwarf 
branches  are  formed  where  portions  of  the  thallus 
have  been  torn  away.     Do  you  find  instances  of 
this  in  the  material  at  hand? 

G.  Sexual  Reproduction: 

1.  The  sexual  reproductive  organs  of  Fucus  are  borne 
in  fertile  conceptacles,  imbedded  in  the  cortical 
tissue  of  the  receptacles.     In  Fucus  vesiculosus  the 
conceptacles  containing  the  female  organs  are  on 
different  plants,  i.e.,  the  plants  are  dioecious.     In 
other  species  they  are  both  on  the  same  plant,  while 
in  still  other  species  (e.g.,  F.  edentatus)  both  kinds 
of  organs  are  in  the  same  conceptacle.     In  the  two 
latter  cases  the  plants  are  monoecious. 

2.  The  Male  Conceptacles: 

(a)  Examine    a    longitudinal    section    of    a   male 
conceptacle,  passing  through  the  ostiole.     Note 
the  outline  of  the  cavity.     Describe  its  wall. 

(b)  Observe  the  filaments  (paraphyses)  within  the 
cavity,    and    describe    the    length,    diameter, 
shape,  and  structure  of  one  of  them.     Do  any 
of  these  filaments  project  through  the  ostiole? 
Explain  the  feeling  as  a  receptacle  is  taken  be- 
tween the  thumb  and  fingers. 

(c)  Are  the  filaments  that  pass  through  the  ostiole 
similar  to  those  that  do  not?     On  the  latter 
observe  the  small  ellipsoidal  organs  antheridia. 
Where    and    how    are    they    attached?     How 


100  MORPHOLOGY  AND   LIFE   HISTORY 

many  on  each  hair?     Observe  their  contents, 
the  sperms  (antherozoids,  spermatozoids) . 
(d)  Make  a  drawing  at  least  50  mm.  in  longest 
diameter,  illustrating  all  the  above  structures. 

3.  The  Female  Conceptacles: 

(a)  Study  a  longitudinal  section  passing  through 
a  female  conceptacle,  as  directed  above 
(G,  2).     Compare  them  in  all  points  with 
the  male  conceptacles. 

(b)  Observe  the  egg-bearing  organs,  oogonia. 
Describe  their  shape,  size,  color,  place  and 
mode    of   attachment,    and   number,    and 
compare  them  in  these  respects  with  the 
antheridia. 

(c)  Describe  the  structure  of  the  wall  of  the 
oogonium,  noting  especially  whether  it  is 
composed  of  cells. 

(d)  Study  the  contents  (oospheres,  or  eggs)  of 
the  oogonium.     How  many  are  there? 

(e)  Make  drawings  showing  all  these  points, 
as  directed  in  G,  2(d). 

4.  The  Fertilization  of  the  Egg: 

(a)  Observe  fresh  plants  that  have  been  hang- 
ing in  the  air  for  about  six  hours,  and  see 
if  you  can  observe  an  orange-colored  fluid 
exuding  from  the  ostioles  of  the  male  con- 
ceptacles. If  so,  mount  some  of  this  fluid 
in  sea-water  and  examine  it  under  the  high 
power. 

(ft)  Note  the  antheridia  floating  about,  and  the 
escaped  sperms.  Do  the  latter  possess  the 
power  of  locomotion?  If  so,  how  do  they 
move?  Describe  their  shape,  relative  size, 
and  color. 


FUCUS  VESICULOSUS  3  OI 

(c)  Make  a  drawing  of  three  or  four  sperms, 
with  the  body  about  10  mm.  long. 

(d)  In  a  similar  way,  find  the  fluid  exuding 
from  the  female  conceptacles.     What  is  its 
color?    Mount  a  drop  of  it  in  sea-water 
and  examine  with  the  high  power. 

(e)  Do  you  find  any  oogonia?    Any  free  eggs? 
If  so,  how  are  the  latter  freed  from  the 
oogonia?     Do  they  possess  the  power  of 
locomotion?     Compare  their  size  with  that 
of  a  sperm. 

(/")  Make  a  drawing  (50  mm.  in  diameter)  of 
an  egg.  By  the  side  of  the  egg  draw  three 
sperms  to  the  same  scale,  showing  the 
relative  size  of  egg  and  sperm. 

(g)  Prepare  a  mount  containing  both  eggs  and 
sperms,  and  endeavor,  if  possible,  to  fol- 
low the  action  of  the  sperms  toward  the 
egg,  and  the  fusion  of  the  two  cells.  With 
what  act  is  fertilization  completed? 

(ti)  Do  you  consider  Fucus  a  more  highly  or  a 
more  lowly  organized  plant  than  Mar- 
chantia?  Give  reasons  for  your  answer. 


Vaucheria  sessilis  (GREEN  FELT) 

A.  Classification: 
Division  I.     Thallophyta. 

Subdivision  I.     Algae. 
Class  II.     Chlorophyceae. 

Order.     Siphonales  (Siphon-algae). 
Family.     Vaucheriaceae. 

Genus.     Vaucheria.     (The  only  genus  in 

the  family.) 
Species,     sessilis. 

B.  Habitat: 

From  your  reading,  class  work,  and  material  at  hand, 
ascertain  and  record  at  this  point  in  your  notes  the 
kind  of  localities  where  this  plant  occurs. 

C.  Naked-eye  Characters: 

Describe  the  color  and  "feel"  of  this  plant,  and  the 
general  form  of  the  plant-body.  What  is  the  signifi- 
cance of  the  common  name  "green  felt"? 

D.  Microscopic  Characters: 

1.  Mount  a  portion  of  the  material  in  water. 

2 .  Is  the  plant  branched  ?    If  so,  is  the  branching  lateral 
or  dichotomous  (i.e.,  forked)? 

3.  Do  you  find  cross- walls?     Does  the  plant  seem  to 
be  composed  of  cells?     What  is  the  outline  of  its 
cross-section? 

4.  Can  you  detect  any  signs  of  division  into  root  and 
shoot?     Do  all  portions  of  the  filaments  appear 
equally  fresh  and  vigorous?     Describe. 

5.  Do  you  find,  on  the  end  of  any  of  the  filaments, 

102 


VAUCHERIA   SESSILIS  103 

holdfasts?     If  so,  describe  them,  and  state  their 
use  to  the  plant. 

6.  Can  you  detect  one  or  more  nuclei?    Any  vacuole 
or  vacuoles?    Any  individual  chromatophores  or 
chloroplasts?     If  so,   what  is  their  position  and 
shape? 

7.  Describe  the  arrangement  of  the  protoplasm  within 
the  filament. 

E.  Physiology: 

1.  Explain  whether,  or  not,  photosynthesis  and  respira- 
tion are  possible  with  this  plant. 

2.  Do  you  find  any  chromatophores  dividing? 

3.  Do  you  find  oil  globules  within  the  plant?     Test 
dechlorophyllized  plants  with  iodine  for  starch. 

4.  How  are  mineral  matter  and  carbon  taken  into  this 
plant?     Explain  the  need  or  lack  of  need  of  special 
structures  for  conducting  food  and  food  elements 
from  one  part  of  the  plant  to  another.     Are  such 
structures  present? 

5.  Why  is  the  plant  not  crushed  by  the  weight  of  the 
water  (when  it  grows  in  water),  or  by  the  cover- 
glass? 

6.  Can  you  detect  any  movement  of  the  protoplasm? 
Observe  carefully  on  this  point. 

7.  Make  careful  drawings  showing  all  features  to  which 
attention  has  been  directed  under  D,  and  E,  2. 

F.  Asexual  Reproduction: 

1.  Carefully  examine  the  tips  of  numerous  filaments 
and  see  if  you  find  any  of  them  slightly  enlarged, 
and  cut  off  from  the  rest  of  the  filament  by  a  cross- 
wall.     Such  a  differentiated  portion  of  the  thallus 
of  Vaucheria  is  a  sporangium ;  its  contents  a  spore. 

2.  If  you  are  fortunate  enough  to  have  material  at  a 
suitable  stage  of  development,  you  may,  by  care- 


IO4  MORPHOLOGY  AND   LIFE   HISTORY 

ful  observation,  observe  a  spore  escaping  from  the 
opening  in  the  tip  of  the  sporangium.  If  so,  give 
careful  attention  to  the  mode  of  locomotion  of  the 
spore,  and  describe  how  its  locomotion  is  accom- 
plished. Since  it  has  motion  (as  animals  do)  it  is 
called  a  zob'spore.  The  zoospore  soon  comes  to 
rest. 

3.  If   the  material   contains   germinating  zoospores, 
carefully  describe  them. 

4.  Make  drawings  illustrating  all  you  have  observed 
under  F. 

G.  Sexual  Reproduction: 

i.  In  " fruiting"  material,  observe  the  lateral  organs 
that  bear  the  gametes.  These  are  the  reproductive 
organs.  As  is  seen,  they  are  of  two  kinds. 

2.  The  larger,  oval-shaped  organ  is  called  theob'gonium. 

Is  the  oogonium  cut  off  from  the  parent  filament 
by  a  wall?  On  one  side  observe  the  rostrum,  or 
beak,  through  which  is  an  opening  or  pore.  In 
material  at  a  suitable  stage  may  be  observed  a 
portion  of  the  contents  of  the  oogonium  being 
voided  or  discarded.  The  protoplasm  that  re- 
mains in  the  oogonium  now  becomes  organized  into 
the  larger  gamete  or  egg  (oosphere).  Is  its  wall 
composed  of  cells,  or  is  it  a  unicellular  organ? 

3.  By  the  side  of  the  oogonium1  find  a  slender  branch, 
usually  recurved  at  the  end.     Is  this  branch  cut  off 
from  the  parent  filament  by  a  wall?     Is  the  tip 
cut  off  from  the  rest  of  the  branch?     This  tip  bears 
small  gametes,  that  swim  about  by  means  of  two  lash- 
like  cilia.    They  are  the  spermatozoids  or  sperms. 

1  If  the  species  is  V.  geminata,  instead  of  V.  sessilis,  the  reproductive 
organs  will  be  found  on  the  same  lateral  branch.  The  above  directions 
will  not  apply  in  detail  to  any  species  except  V.  sessilis. 


VAUCHERIA   SESSILIS 

What  is  the  organ  that  bears  the  sperms  called? 
The  base  of  the  antheridial  branch  is  the  pedicel, 
or  stalk. 

4.  Can    you    detect    any    sperms    escaping?     If    so, 
observe  and  describe  them  carefully.     See  if  you 
can  find  any  empty  antheridia. 

5.  Make  careful  drawings  showing  all  points  observed 
under  G. 

6.  Is  there  a  division  of  physiological  labor  in  Vauch- 
eria?     Explain  in  detail. 

7.  Show,  by  a  diagram,  the  life  cycle  of  Vaucheria. 

8.  State    the    difference    between    conjugation    and 
fertilization. 

9.  Draw  an  ideal  diagram  of  a  complete  plant,  showing 
all  structures,  and  stages  of  their  development. 


Spirogyra  sp.  (POND  SCUM,  GREEN  siLK)1 

A.  Classification: 
Division  I.     Thallophyta. 

Subdivision  I.    Algae. 
Class  II.     Chlorophyceae. 
Order.     Conjugales. 
Family.     Zygnemaceae. 
Genus.    Spirogyra. 
Species,     sp.  (i.e.,  not  determined). 

B.  Habitat: 

Ascertain  from  your  own  observations  and  from  the 
text,  and  record  at  this  point  in  your  notes,  the  habitat 
of  Spirogyra. 

C.  Physiology: 

1.  Explain,  clearly  but  concisely,  how  the  bodily  form 
of    this   plant   is    maintained.     Account   for   any 
variations  in  the  shape  of  the  cells. 

2.  Do  you  find  any  roots  or  other  organs  for  anchoring 
the  plant  to  the  substratum?     Do  you  think  the 
plant  is  suitably  organized  for  growing  in  running 
water?     Explain.     State  a  reason  why  roots  are 
not  necessary  for  this  plant. 

3.  Explain  the  presence  or  absence  of  stomata.     Do 
you  find  a  cuticle?     Is  photosynthesis  possible  with 
Spirogyra?     Respiration?     Explain. 

1  The  morphological  characters  of  this  plant  have  already  been  studied 
(pp.  11-15).    They  should  now  be  carefully  reviewed,  preparatory  to  the 
consideration  of  the  physiology  and  reproduction  of  the  plant. 

2  True  cuticle  does  not  occur,  but  a  modification  of  the  outer  portion 
of  the  cell-wall,  called  the  sheath,  and  which  gives  the  plant  its  slippery 
"feel,"  is  similar  to  cuticle,  though  not  identical  with  it.     This  sheath 
is  difficult  to  observe  directly,  though  it  may  sometimes  be  identified  on 
the  outside  of  the  filament  at  the  places  where  the  cross-walls  occur. 

106 


SPIROGYRA   SP.  107 

4.  Can  you  detect  any  difference  between  the  cells 
physiologically?     From  your  own  observations  do 
you  think  there  is  any  correlation  between  the  struc- 
ture of  cells  and  their  function?     Explain  clearly. 

5.  Is  there  any  evidence  in  Spirogyra  of  a  correlation 
between  structure  and  env  ronment?     Explain. 

D.  Asexual  Reproduction  in  Spirogyra: 

i.  From  what  you  have  already  learned  of  Spirogyra, 
state  the  possibilities  of  vegetative  propagation  in 
this  plant. 

E.  Sexual  Reproduction  in  Spirogyra: 

1.  Use  fresh  material,  if  possible;  otherwise  preserved 
specimens,  or  prepared  slides. 

2.  Observe  the  various  stages  in  the  fusion  of  two  cells 
(gametes).     Do  the  fusing  gametes  belong  to  the 
same,    or    to    different    filaments?     Observe    the 
conjugation-tubes  connecting  adjacent  filaments.1 
What  is  their  function?     Their  relative  diameter? 
Try  to  find  tubes  in  various  stages  of  formation. 
Are  their  distal  ends  open  before  they  come  into 
contact?     How  is  the  opening  made?     Do  the  tubes 
grow  together  or  merely  touch  each  other? 

3.  Does  conjugation  seem  to  be  a  function  of  all  the 
cells  of  the  filament,  or  of  certain  cells  only? 

4.  Do  the  gametes  pass  from  either  filament  to  the 
other,  or  do  the  cells  of  a  given  filament  all  behave 
alike    in    this    respect?     In    this    connection    see 
whether  all  the  zygospores  occur  in  one  filament, 
or  not. 

1  The  form  of  conjugation  described  in  the  outline  above,  is  termed 
" scalarif orm "  (ladder-like).  Another  type,  known  as  "lateral"  con- 
jugation may  frequently  be  met  with,  in  which  the  gametes  are  formed  by 
adjacent  cells  of  the  same  filament.  In  less  frequent  cases  the  protoplast 
of  a  single  cell  organizes  itself  into  a  reproductive  body  (aplanospore) 
without  conjugation.  This  process  is  a  type  of  parthenogenesis. 


108  MORPHOLOGY  AND   LIFE   HISTORY 

5.  Does  the  cell -wall  of  the  receiving  cell  serve  as  the 
cell-wall  of  the  zygospore,  or  does  the  latter  form  a 
new  wall? 

6.  In  a  sentence  define  the  term  supplying  cell,  using 
the  words  gamete  and  conjugation. 

7.  If  fresh  material  is  studied,  describe  any  observed 
differences  in  color  between  the  mature  zygospore 
and  the  non-conjugating  cells;  any  structural  dif- 
ferences between  the  cells  of  a  supplying  filament 
and  those  of  a  receiving  filament.     Do  you  observe 
any   evidence    of    sexual    differentiation    in    the 
filaments? 

8.  Explain  whether  Spirogyra  represents  a  condition 
of  isogamy  or  of  heterogamy. 

9.  Make  drawings  of  all  the  following  features  shown 
by  your  material,  with  each  cell  about  50  mm.  long. 

(a)  Two  adjacent  cells  in  which  the  conjugation- 
tubes  are  just  beginning  to  develop. 

(b)  Two  adjacent  cells  in  which  the  conjugation- 
tubes  have  just  met. 

(c)  Two  adjacent  cells  in  which  the  active  (supply- 
ing) gamete  is  passing  through  the  conjugation- 
tube. 

(d)  Two  adjacent  cells  in  which  the  passage  is 
complete. 

(e)  Two  adjacent  cells  after  conjugation  is  com- 
plete.    Show  carefully  and  accurately  the  details 
of  structure  of  the  zygospore. 

10.  Study  stages  in  the  germination  of  the  zygospore 
as  shown  on  the  chart.  State,  in  order,  the  proc- 
esses that  take  place  in  the  formation  of  the 
new  plant  (mature  zygote)  from  the  zygospore. 
Compare  the  plant  of  the  new  generation  with 
its  parents. 


SPIROGYRA   SP.  IOQ 

11.  Is  there  a  physiological  division  of  labor  in  this 
plant?     Explain  in  detail. 

12.  Draw  a  diagram  showing  the  ancestors  of  a  plant 

of  Spirogyra  for  three  generations. 

13.  To  complete  your  notes  on  Spirogyra,  write,  at 
home,  and  before  the  next  laboratory  period,  as 
clear  and  well -worded  an  account  as  you  can  of 
the  life  history  of  the  plant. 

14.  Arrange    ferns,    algae,    mosses,    liverworts,    in    a 
vertical  column  in  the  order  of  the  complexity  of 
their  organization,  placing  the  more  highly  organ- 
ized near  the  top  of  the  column.     Write  a  clear 
statement   of  the  reasons  for  your  arrangement 
of  the  above  classes. 


Pleurococcus  vulgaris  (GREEN  SLIME) 

A.  Classification: 
Division  I.     Thallophyta. 

Subdivision  I.     Algae. 

Class  II.     Chlorophyceae  (green  algae). 
Order.     Ulotrichales. 

Family.     Chaetophoraceae. 
Genus.    Pleurococcus. 
Species,     vulgaris  Menegh. 

B.  Habitat: 

i.  From  the  material  given  you,  infer  where  this  plant 
grows.  Leave  a  blank  space  in  your  note-book, 
and  before  the  next  laboratory  period,  record  further 
observations  on  this  point,  made  out  of  doors, 
noting  especially  the  following  points.  Does  the 
plant  appear  to  be  more  abundant  on  one  side  of 
the  object  on  which  it  grows  than  on  another? 
Describe  and  explain.  In  general,  what  external 
conditions  seem  to  favor  its  growth?  Do  you  ever 
find  it  intimately  associated  with  other  plants? 
Describe. 

C.  Naked-eye  Characters: 

i.  Describe  the  color  of  a  colony  of  Pleurococcus. 
Can  you  distinguish  the  shape  or  other  characters 
of  an  individual  plant? 

D.  Microscopic  Characters: 

i.  With  the  needle  carefully  scrape  off  a  bit  of  the 
plant  from  a  piece  of  moist  bark  or  wood,  and 
mount  it  in  water. 

no 


PLEUROCOCCUS  VULGARIS  III 

2.  Is  the  body  of  this  plant  differentiated  into  root, 
stem,  and  leaves?    Is  it  composed  of  cells?    If  so, 
of  how  many?     Make  a  thorough  study  of  this 
point  before  you  answer   and  thoroughly  consider 
how  many  cells  you  think  are  necessary  in  order  to 
make  one  plant.     State  your  opinion,  with  reasons. 
Compare  the  arrangement  of  the  cells  with  those  in 
Spirogyra. 

3.  Describe  the  color  and  shape  of  individual  cells. 
Descr  be  and  account  for  any  variations  observed 
in  the  shape  of  the  cells. 

4.  Carefully    describe    all    the    cell-organs    you    can 
identify  in  this  specimen.     Name  all  the  cell-organs 
you  cannot  find.     How  does  the  chlorophyll  occur 
in  the  cell  of  Pleurococcus?     If  you  find  chloroplasts 
state  how  many,  their  location,  and  relative  size. 

5.  Make  careful  drawings  showing  all  features  so  far 
as  observed,  with  none  of  the  cells  less  than  15  mm. 
in  longest  diameter. 

Physiology: 

1.  How  does  Pleurococcu    remain  fixed  to  the  sub- 
stratum on  which   it   grows?     Are   there  special 
organs  for  this  purpose? 

2.  Are  there  special  organs  for  the  taking  in  of  nourish- 
ment from  the  substratum?    How  can  the  plant 
accomplish  this  process? 

3.  Is  photosynthesis  possible  with  Pleurococcus?     Give 
reasons  for  your  answer.    Are  stomata  present? 
Why?    Describe  how  C02  can  be  taken  into  the 
cell. 

4.  Are  there  any  special  organs  of  respiration?    How 
can  this  process  take  place? 

5.  Do  you  think  Pleurococcus  is  sensitive  to  stimuli 
from  without?     Give  reasons  for  your  answer. 


112  MORPHOLOGY  AND   LIFE  HISTORY 

F.   Reproduction: 

1.  Do  you  find  any  cells  that  appear  to  be  dividing? 
If  so,  carefully  describe  their  appearance.     What 
are  the  indications  that  a  cell  is  dividing? 

2.  Do  the  cells  tend  to  remain  united  after  cell  divi- 
sion?    Is  this  true  of  all  of  them?    Describe. 

3.  Make  three  diagrams,  showing  (a)  the  life  cycle  of  a 
Pleurococcus  plant;  (b)  the  descendants  of  one  plant 
for  six  generations;  (c)  the  ancestors  of  one  plant  for 
six  generations. 

4.  Is  there  a  division  of  physiological  labor  in  this 
plant,  or  are  all  life  functions  performed  by  every 
cell? 


Phycomyces  nitens  (or  Rhizopus  nigricans) 

A.  Classification: 

Division  I.     Thaliophyta. 
Subdivision  B.     Fungi. 

Class  III.     Phycomycetes  (alga-fungi). 
Order.     Mucorales  (the  molds) . 
Family.     Mucoraceae. 
Genus.    Phycomyces. 
Species,    nitens. 

B.  Habitat: 

i.  Upon  what  substratum  is  the  Phycomyces  growing? 
What  atmospheric  condition  seems  to  be  most 
favorable  to  its  growth? 

C.  Naked-eye  Characters: 

1.  Describe  in  detail  the  appearance  of  this  plant  as 
it  grows.     What  is  its  color?     Describe  any  varia- 
tions in  color. 

2.  Note  the  aerial  filaments  or  hyphae.     Do   they 
grow    erect   or   horizontally?     How    many    milli- 
meters long  are  they? 

3.  On  the  ends  of  some  of  them  observe  the  enlarged 
structure,    the   sporangium.    Describe   its   shape. 
From  its  name,  sporangium,  what  do  you  infer  that 
it    contains.     Hyphae    that    bear    sporangia    are 
sporangiophores.     What   does   the   term  literally 
mean? 

4.  Compare  the  height  of  the  sporangiophores  bearing 
young  (yellowish)   sporangia,  with  that  of  those 
bearing    more    mature    (dark-colored)    sporangia. 
Explain  the  significance  and  advantage  of  this. 

5.  Using  the  hand  lens,  note  the  vegetative  hyphae 
s  .  113 


114  MORPHOLOGY  AND   LIFE   HISTORY 

that  grow  into  the  substratum  (substance  on  which 
the  fungus  grows),  and  over  its  surface.  These 
filaments  constitute  the  mycelium.  Compare  their 
diameter  with  that  of  the  sporangiophores.  Do 
they  appear  to  branch? 

6.  Make  a  drawing,  illustrating  all  points  observed. 
Make  a  diagram  showing,  in  order,  the  relative 
heights  of  six  sporangia  of  various  ages.  Indicate 
the  scale  used. 

D.  Vegetative  Propagation: 

1.  If  Rhizopus  nigricans  is  used,  study,  with  the  naked 
eye,  the  formation  of  stolons  by  this  plant,  and 
describe  in  full,   with  drawings,   this  process  of 
propagation.     This  plant  (Rhizopus  nigricans)  was 
at  one  time  called  Mucor  stolonifer.    Explain  the 
appropriateness  of  this  latter  specific  name.     The 
generic  name,  Rhizopus  (root-like  foot),  refers  to 
the  branching  mycelial  hyphae,  which  form  at  the 
tips  of  the  stolons.     Explain  the  significance  of  the 
specific  name  nigricans  (black). 

2.  How  does  Phy corny ces  nitens  increase  vegetatively? 

3.  Study  and  draw  stages  in  the  germination  of  spores 
that  have  been  in  sugar  solution  for  twenty-four 
hours.     (Use  spores  of  Phy  corny  ces  or  Sporodinia, 
as  spores  of  Rhizopus  do  not  germinate  readily  in 
sugar  solution.) 

E.  Microscopic  Characters  of  the  Mycelium: 

1.  Mount  in  water  a  small  portion  of  the  substratum 
with  the  mold  attached,  and,  if  necessary,  very 
carefully  tease  it  out  with  the  needles. 

2.  Study  the  mycelium.     Is  it  branched?     Are  the 
mycelial  hyphae  of  the  same  diameter  throughout? 
Are    cross-walls    present?     If    so,    describe    their 
frequency. 


PHYCOMYCES   NITENS  115 

3.  Make  a  drawing  to  illustrate  the  above  points. 

F.  Physiology: 

1.  Describe    the    color    of    the    sporangiophore    and 
sporangium  as  seen  under  the  microscope,  and  state 
whether  this  color  is  in  the  cell-wall  or  in  the  cell- 
contents. 

2.  If  you  detect  any  motion  of  the  protoplasm  (best 
seen  in  young  sporangiophores)  describe  it  accu- 
rately.    Is  it  a    true  circulation  (i.e.,  in  various 
directions  in  a  closed  circuit),  a  rotation  (i.e.,  up 
one  side  of   the  filament  and  down  the  other), 
or  a  streaming  (i.e.,  all  currents  apparently  toward 
one  and  the  same  end  of  the  filament).     Suggest 
any  advantage  this  motion  would  be  in  the  nourish- 
ing of  the  plant;  in  the  formation  of  sporangia. 

3.  Make  a  drawing  of  a  portion  of  the  hypha,  at  least 
15  mm.  wide,  showing  the  appearance  of  the  con- 
tents, and,  with  arrows,  the  direction  of  motion. 

4.  What  foods  does  this  fungus  need?     From  where 
must  they  be  obtained?    Are  they  soluble?     Can 
Phycomyces  take  in  solid  food?    What  process  is 
necessary  in  our  own  bodies  before  we  can  utilize 
solid    food?     Must    Phy  corny  ces    perform    a    like 
function?     Is   there   a   special   organ   for   such  a 
function?     Must  the  process  go  on  inside  or  out- 
side of  the  body  of  the  plant?     Why? 

5.  Is  photosynthesis  possible  with Phycomyces?    Why? 
How  must  it  get  its  carbohydrates? 

6.  Does  Phycomyces  respire?     Give  a  reason  for  your 
answer. 

7.  What  is  the  most  obvious  and  important  difference 
between  the  cells  of  Phycomyces  and  of  Spirogyra? 

G.  Asexual  Reproduction: 

i.  Study  a  sporangiophore.    Is  it  of  the  same  diameter 


Il6  MORPHOLOGY  AND   LIFE   HISTORY 

throughout?    Are   cross-walls   anywhere   present? 
If  so,  describe  their  location. 

2.  Is  the  sporangium  borne  on  the  tip  of  the  sporangio- 
phore,  or  at  one  side?    Are  its  contents  separated 
from   those  of   the  sporangiophore?     If  so,  how? 
Compare,  on  this  point,  young  and  old  sporangia. 
Is  there  more  than  one  sporangium  on  a  sporangio- 
phore?    Within  the  wall  of  the  sporangium  observe 
the  central  columella,  surrounded  by  the  spores. 
Describe   the   shape   of   the   columella.     Are    the 
spores  numerous  or  few  within  one  sporangium? 
Look  for  cases  where  the  wall  of  the  sporangium, 
has  ruptured,  and  the  spores  are  mostly  scattered, 
leaving  the  columella  naked. 

3.  Illustrate  by  drawings  all  features  observed  under 
Gj  i  and  2.     Make  the  sporangium  at  least  20  mm. 
in  diameter. 

4.  Describe  the  shape,  relative  size,  color,  and  surface 
markings  (if  any)  of  the  spores. 

H.  Sexual  Reproduction: 

NOTE. — For  this  study  Sporodinia  may  be  substituted, 
as  it  more  readily  yields  suitable  material. 

1.  Find  conjugating  branches.     Describe  their  shape. 

2.  Find  mature  conjugating  branches  with  the  end 
contents  cut  off  to  form  gametes.    The  remainder 
of  the  branch  is  now  called  a  suspensor. 

3.  Find,  on  still  more  mature  material,  the  gametes 
fused.    What   is   the   resulting   structure   called? 
Describe  its  appearance.     If  the  material  is  suitable, 
describe  the  germination  of  this  structure. 

4.  Illustrate  with   a   drawing   all  features   observed 
under  H.     Make  the  suspensors  at  least  25  mm. 
long,  and  other  structures  in  proportion. 


Saprolegnia  (WATER  MOLD) 

A.  Classification: 

Division  I.     Thallophyta. 
Subdivision  B.     Fungi. 
Class  III.    Phycomycetes. 
Order.     Saprolegniales. 
Family.     Saprolegniaceae. 
Genus.     Saprolegnia. 
Species,     sp.  (i.e.,  not  given). 

B.  Habitat: 

i.  The  spores  of  this  fungus  are  widely  distributed, 
and  develop  readily  under  suitable  conditions. 
Such  conditions  are  realized  when  a  dead  fly  is 
placed  in  a  dish  of  tap-water.  The  fungus  will  be 
sufficiently  developed  for  study  within  five  to  seven 
days. 

C.  Naked-eye  Characters: 

1.  Carefully  observe  the  aerial  hyphae  as  they  grow, 
forming  a  halo  about  the  body  of  the  fly.     What  is 
the  diameter  of  the  halo?    Its  shape?     Does  its 
shape  seem  to  be  influenced  by  the  shape  of  the  fly's 
body?    Do  the  filaments  grow  vertically  upward 
and  downward  or  only  horizontally?     What  is  the 
color  of  the  halo? 

2.  Estimate  the  average  length  of  the  hyphae. 

3.  Can  you  detect  any  evidences  of  the  formation  of 
sporangia  at  the  tips  of  some  of  the  hyphae,  and  of 
sexual  reproductive  organs  near  the  body  of  the  fly? 
Use  a  hand  lens  if  necessary. 

117 


Il8  MORPHOLOGY  AND   LIFE   HISTORY 

4.  Make  a  drawing,  about  25  mm.  in  longest  diameter, 
showing  the  appearance  of  this  fungus  as  it  grows  on 
the  body  of  the  fly. 

D.  Microscopic  Characters: 

1.  With  the  needle  or  scalpel  carefully  remove  a  few 
filaments   and   mount   them   in  water.     Examine 
with  the  low  power. 

2.  Make  careful  comparisons  of  the  tips  of  hyphse 
enlarged  to  form  sporangia  with  those  not  thus 
modified.    Describe  the  appearance  of  the  contents 
in  each. 

3.  Do  you  find  any  cross- walls  in  the  filaments? 

4.  Do  you  find  vacuoles?    Plastids?    Nuclei? 

5.  Make  a  drawing  showing  the  appearance  of  the  tip 
of  a  vegetative  filament  (10  mm.  in  diameter). 

E.  Nutrition  and  Growth: 

1.  See  if  you  can  find  hyphse  bearing  empty  sporangia. 
If  so,  do  you  find  the  hypha  continuing  its  growth 
in  length  within  the  empty  sporangium?    Illus- 
trate this  point  by  a  drawing. 

2.  Where  do  the  vegetative  hyphae  (mycelium)  grow? 
Describe  the  nature  of  the  surface  of  the  fly's 
body.    How  can  the  delicate  mycelia  penetrate  to 
the  interior  of  the  fly? 

3.  Upon  what  does  this  fungus  feed?    State  in  detail 
the  necessary  steps  in  the  process  of  getting  this  food 
into  the  interior  of  the  mycelium.    In  this  connec- 
tion make  comparisons  with  Phycomyces  (see  F,  4, 
under  Phycomyces,  p.  115). 

4.  Is  there  any  correlation  here  between  the  absence  of 
chlorophyll  and  the  habitat  of  the  plant?    If  so, 
explain  and  compare  with  Phycomyces^  and  with 
Spirogyra. 


SAPROLEGNIA  119 

F.  Asexual  Reproduction: 

1.  Carefully    study    again    the    terminal    sporangia. 
How  many   times   longer   than  broad  are   they? 
Compare  the  thickness  of  the  sporangium  walls 
with  those  of  the  remainder  of  the  hyphae.     Can 
you  detect  any  variations  in  the  thickness  of  the 
sporangium  walls?     If  so,    describe    and    explain. 
Describe  and  account  for  the  shape  of  the  free  tip 
of  the  sporangium. 

2.  Describe  the  shape  of  the  zoospores,  or  swarm- 
spores;    their   size;   number   in   one   sporangium; 
color.     Are  they  all  alike  in  these  characters? 

3.  Endeavor  to  find  swarm-spores  escaping  from  a 
sporangium.     Do  they  merely  float  away,  or  have 
they  power  of  locomotion?    Look  for  organs  of 
locomotion?     If    you    find    them,    describe    their 
number,  length,  action,  and  general  appearance. 
Do  they  precede  or  follow  the  zoospore  as  it  moves 
through  the  water? 

4.  Do  the  zoospores  ever  move  up  or  down  through 
the  water  so  as  to  be  out  of  focus?     If  so,  consider 
thoughtfully  the  thickness  of  the  film  of  water 
in  which  they  are,  and  try  to  form  some  conception 
of  the  size  of  a  body  that  moves  vertically  beyond 
the  range  of  vision  in  a  film  of  such  a  depth.     Briefly 
discuss  this  point. 

5.  Do  you  see  any  evidence  that  any  two  of  these 
swarm-spores  are  in  the  process  of  fusion?    Do 
their  movements  appear  to  be  directed,  or  not? 

6.  Make   suitable   drawings   to   illustrate   all   points 
observed  under  F. 

G.  Sexual  Reproduction: 

i.  Under    suitable    conditions    female    reproductive 
organs,  oogonia,  develop  on  certain  hyphae  near  the 


120  MORPHOLOGY   AND   LIFE   HISTORY 

body  of  the  fly,  and  each  oogonium  develops  a 
number  of  eggs.  If  oogonia  are  found,  describe 
them  carefully  as  directed  above  (F,i )  for  sporangia, 
making  suitable  drawings.  Do  they  always  occur 
at  the  end  of  the  hypha  that  bears  them? 
2.  The  male  reproductive  organs  are  antheridial  fila- 
ments, growing  either  below  the  oogonia  or  on 
adjacent  hyphae.1  They  are  of  smaller  diameter 
then  the  hyphae.  If  you  find  these  organs,  care- 
fully describe  their  appearance,  contents,  size,  and 
relation  to  the  oogonia.  Illustrate  all  points  ob- 
served with  suitable  drawings. 
H.  General  Questions: 

1.  Do  you  find  a  physiological  division  of  labor  in 
Saprolegnia?    If  so,  describe  in  detail. 

2.  State  why  you  consider  this  plant  higher  or  lower  in 
in  the  scale  of  life  than  Phycomyces  or  Fucus. 

3.  Describe  all  methods  of  dissemination  of  Saprolegnia 
that  you  can  think  of. 

xThe  development  of  the  egg-cell  without  fertilization  (i.e.,  by  par- 
thenogenesis) is  more  usual  than  fertilization  in  Saprolegnia,  so  that  fer- 
tilization, or  even  antheridial  filaments,  may  be  wanting. 


Albugo  Candida1  (BLISTER  BLIGHT) 

A.  Classification: 
Division  I.     Thallophyta. 

Subdivision  II.     Fungi. 
Class  V.     Phycomycetes. 
Order.     Peronosporales. 
Family.     Peronosporaceae. 
Genus.     Albugo. 
Species.    Candida. 

B.  Habitat: 

This  fungus  is  parasitic  on  plants  belonging  to  the 
mustard  family  (Cruciferae) .  It  causes  the  "  blister- 
blight,"  or  "  white  rust/'  on  the  leaves  and  stems 
of  the  shepherd's  purse  (Capsella  bursa-pastoris) 
and  often  on  the  radish. 

C.  Naked-eye  Characters: 

1.  Describe  the  appearance   (color,  shape,  size,  etc.) 
of  the  blisters  formed  by  this  parasite  on  the  host- 
plant.     What  organs  of  the  host  are  affected? 

2.  Make    drawings,    natural    size,    showing    all    the 
features  observed. 

D.  Microscopic  Characters: 

1.  Study  cross-sections  of  the  host-plant  taken  through 
one  of  the  blisters. 

2.  What  causes  the  blisters?    In  what  tissue  or  tissues 
of  the  host  does  the  mycelium  grow? 

E.  Nutrition  and  Growth: 

1.  In  what  form  must  carbon  be  supplied  to  this  plant? 
Why? 

2.  In  thin  sections  look  for  absorbing  organs  (haus- 
toria) ,  branching  from  the  mycelium  and  penetrating 

1  Cystopus  -candidus  (Pers.)  Lev. 

121 


122  MORPHOLOGY  AND   LIFE   HISTORY 

through  the  cell-walls  into  the  cells.1  Describe 
their  relative  length,  shape  and  general  appearance. 
How  far  do  they  project  into  the  cells?  What  do 
you  infer  is  the  function  of  these  organs?  Suggest 
a  way  in  which  they  might  be  able  to  pierce 
the  cell-wall.  What  other  function  must  they  per- 
form besides  the  one  you  have  already  mentioned? 

3.  Where  and  how  does  this  plant  digest  its  food? 
What  foods  does  it  need?    What  is  their  source? 

4.  Is  there  any  correlation  between  the  absence  of 
chlorophyll  and  the  habitat  of  this  plant?     Explain, 
and  compare  with  Phycomyces  and  Marchantia. 

5.  Make  a  drawing  showing  three  cells  of  the  host 
with  the  adjacent  mycelium  and  the  penetrating 
haustoria. 

F.  Asexual  Reproduction: 

1.  Observe  the  chains  of  spores  (conidia,  or  conidio- 
spores).     On  what  are  they  borne?     Describe  their 
shape,  color,  size.    Are  they  all  of  the  same  size? 
Which  is  the  youngest  conidium  in  a  chain?     Why 
do  you  think  so  ?     Of  how  many  cells  is  each  conidium 
composed?    Are  they  attached  to  each  other?    If 
so,  how? 

2.  Observe  the  conidia-bearing  hyphae  (conidiophores) . 
Describe  their  shape,  and  the  appearance  of  their 
contents.     Do    they    have    cross- walls?    Observe 
this  last  point  carefully,  and  describe. 

3.  Describe  in  detail,  from  your  own  observations, 
the  method  of  formation  of  the  conidia. 

4.  Make  one  drawing  showing  all  points  observed, 
including  the  tissues  of  both  host  and  parasite. 

5.  Make    a  second  drawing  of  two   conidiophores, 

1  The  haustoria  are  difficult  to  identify,  especially  with  poor  sections, 
and  too  much  time  should  not  be  spent  in  trying  to  detect  them. 


ALBUGO   CANDIDA  123 

showing  the  attached  chains  of  conidia  and  the  mode 
of  formation  of  the  latter.    In  this  drawing  make 
the  conidia  at  least  5  mm.  in  diameter. 
6.  Include  in  your  notes  at  this  point  a  brief  descrip- 
tion of  the  germination  of  the  conidia.     (The  infor- 
mation   should,    if    possible,    be    obtained    from 
material  supplied  by  the  instructor,  otherwise  from 
lecture  or  reading.) 
G.  Sexual  Reproduction: 

1.  The  sexual  reproduction  of  Albugo  generally  occurs 
in  other  parts  of  the  host-plant,  and  later  in  the 
season  than  the  asexual  reproduction.     The  tissues 
of  the  host-plant  containing  the  sexual  organs  of  the 
parasite  are  generally  enlarged  (hypertrophied)  and 
distorted. 

2.  In  the  material  given  you  observe  the  large  spherical 
oogonium,  containing  a   single  oosphere  or  egg 
surrounded  by  the  so-called  periplasm  or  epiplasm. 
Is  the  oogonium  sessile  or  stalked? 

Closely  appressed  to  the  oogonium  at  some  point 
find  the  smaller  antheridium.  Describe  its  shape, 
and  general  appearance.  Are  its  contents  separated 
from  those  of  the  hypha  by  a  cross- wall? 

4.  How  does  the  male  gamete  (sperm)  pass  through 
the  oogonium- wall  and  periplasm  to  the  egg? 

5.  If  your  material  is  suitable,  observe  and  describe 
the  mature  fertilized  egg  (ob'sperm).    After  fertili- 
zation the  periplasm  becomes  transformed  into  the 
wall  of  the  oosperm.    Note  the  exospore  (of  one 
layer)  and  the  endospore  of  three  layers. 

6.  Make  drawings  showing  all  features  observed  un- 
der G. 

H.  General  Questions: 

i.  Explain  how  Albugo  is  disseminated. 


124  MORPHOLOGY  AND   LIFE   HISTORY 

2.  What  weather  conditions  would  favor  its  dissemina- 
tion? 

3.  The  blight  caused  by  Albugo  is  difficult  to  eradicate. 
What  characteristic  of  the  plant  helps  to  explain 
this  fact? 

4.  Classify  the  Phycomycetes  you  have  studied  as 
either  Zygomycetes  (Section  i),  or  Oomycetes  (Sec- 
tion 2),  and  give  a  reason  for  your  classification. 
Give  the  literal  meaning  of  these  two  new  terms. 


Agaricus  campestris  (MEADOW-MUSHROOM)  1 

A.  Classification: 
Division  I.     Thallophyta. 

Subdivision  B.     Fungi. 

Class  V.    Basidiomycetes.  .  ." 

Series.     Eubasidiomycetes  (true  or  typical  Basi- 
diomycetes). 

Sub-class.     Hymenomycetes. 
Order.    Agaricales. 
Family.    Agaricaceae. 
Genus.    Agaricus. 
Species,     campestris. 

B.  Habitat: 

i.  From  your  own  observation,  and  from  the  class 
discussion  and  assigned  readings,  describe  the 
habitat  of  this  plant. 

C.  Naked-eye  Characters: 

1.  Form. — Describe  the  form  of  your  specimen.     If 
specimens  of  different  ages  are  available,  compare 
their  forms  and  describe  any  variations  in  specimens 
of  various  ages.     Is  the  form  of  the  mature  speci- 
men constant?     Is  its  size  constant? 

2.  Color. — Describe  accurately,  noting  especially  any 
variations  in  color. 

3.  Structure. — Note  the  differentiation  of  the  plant- 
body  (thallus)  into  an  expanded  portion  (pileus), 

1  The  outline  for  the  study  of  a  fleshy  fungus  has  been  prepared  with 
special  reference  to  the  meadow  mushroom  (Agaricus  campestris).  It  is 
general  enough,  however,  with  the  exception  of  the  outline  of  classifica- 
tion, to  apply  to  any  gill-bearing  form.  Indicate  in  your  notes  the  exact 
genus  and  species  given  you  for  study. 

"5 


126  MORPHOLOGY  AND   LIFE   HISTORY 

borne  on  a  stalk  or  stipe.    Is  there  a  ring  of  tissue 
(annulus)  around  the  stipe? 

(a)  The  pileus.    Describe  the  shape,  size,  color, 
and  any  characteristic  markings  on  its  upper 
surface.     Examine  carefully  and  describe  the 
margin  of  the  pileus.     Are  there  any  charac- 
teristic elevations  or  depressions  on  the  pileus? 
If  so,  state  how  many  and  where  they  are. 
Compare  the  color  of  the  under  surface  in  young 
and  old  specimens. 

Describe  the  shape,  arrangement,  relative 
number  and  color  of  the  lamellae,  or  gills. 
Are  the  margins  (free  edges)  of  the  gills  entire 
or  notched?  Do  they  extend  clear  to  the  stipe? 
Are  they  attached  to  the  latter?  Do  they  all 
extend  clear  to  the  margin  of  the  pileus? 
Describe  any  variations  in  size.  Count  the 
gills  in  a  space  of  10  mm.,  then  calculate  from 
the  circumference  of  the  pileus  the  total  number 
of  gills. 

(b)  The  stipe.    Describe  its  shape,  and  color,  and 
any  variations  in  color  and  diameter.     Describe 
its  mode  of  attachment  to  the  pileus.    De- 
scribe the  method  of  attachment  of  the  plant 
to  the  substratum.     Is  there  a  mycelium  or 
other  special  means  of  fixation?    If  so,  is  it 
continuous  with  the  tissues  of  the  stipe? 

(c)  The  annulus.    If  an  annulus  is  present,  de- 
scribe its  location  on  the  stipe;  its  structure. 
Compare  its  structure  with  that  of  the  mem- 
brane on  the  edge  of  the  pileus.    What  is  the 
relation  between  the  membrane  and  the  annulus 
in  young  specimens?     When  these  structures 
are  united  they  form  a  veil.     Is  a  veil  present 


AGARICUS   CAMPESTRIS  127 

in  young  specimens  examined  by  you?  What 
do  the  annulus  and  marginal  membrane  repre- 
sent? 

(d)  Make  drawings,  not  less  than  life  size,  of  both  a 
young  and  a  mature  specimen,  as  seen  from  the 
side,  labeling  all  parts. 

(e)  With  a  sharp  scalpel  or  razor  carefully  divide 
your    specimen    longitudinally    through    the 
middle,  and  make  a  drawing  illustrating  all 
features  shown  in  longitudinal  sectional  view. 

(/")   Make  a  third  drawing  showing  the  structure 
and  outline  of  the  stipe  as  seen  in  cross-section, 
and  a  fourth  drawing,  showing  the  outline  of  the 
gill  as  seen  in  cross-section. 
D.  Microscopic  Characters: 

i.  When  suitable  material  is  available,  note  and  de- 
scribe the  mycelium,  extending  through  the  soil. 
2.  The  annulus  and  stipe.  Mount  (in  clearing  fluid 
or  water)  thin  longitudinal  sections  passing  through 
the  stipe.  Is  the  stipe  composed  of  distinct  tissues, 
e.g.,  like  the  hypocotyl  of  Ricinus,  or  the  thallus  of 
Fucus?  If  so,  describe.  Observe  that  the  stipe  is 
composed  of  hyphae.  Of  what  is  the  annulus 
composed,  and  what  is  its  relation  to  the  tissue  of 
the  stipe?  Do  the  hyphae  have  cross-walls  or 
septa?  If  so,  what  angle  do  the  septa  make  with 
the  walls  of  the  hyphae?  Do  the  hyphse  branch? 
Do  you  find  spaces  between  the  hyphae?  If 
so,  describe  their  size  and  distribution.  Make  a 
drawing  to  show  the  features  observed  under  2. 
3.  The  pileus.  Mount  (in  clearing  fluid)  a  thin  longi- 
tudinal section  passing  through  the  stipe,  pileus,  and 
a  portion  of  a  gill.  Examine  under  low  power. 
Can  you  trace  the  hyphae  of  the  stipe  in  to  the  pileus? 


128  MORPHOLOGY  AND  LIFE  HISTORY 

If    so,    describe    their    arrangement    within    the 
pileus.     Do  they  extend  into  the  gills? 
4.  Make  a  diagram,  life  size,  to  illustrate  the  relation 
to  each  other  of  the  hyphae  of  the  mycelium,  stipe, 
annulus,  pileus,  and  gills. 
E.  Reproduction: 

1.  Mount  (in  clearing  fluid  or  water)  thin  cross-sec- 
tions of  a  gill. 

2.  Observe  the  differentiation  of  the  gill  into  a  central 
tissue  or  trama,  an  outer,  spore-bearing  tissue,  or 
hymenial  layer  (hymenium),    and,  between   these 
two,    a   sub -hymenial  layer.     Of  what  are  these 
tissues  composed?     How   are   they    distinguished 
from  each  other?     Show  by  diagram  the  position 
of    these   three  layers. 

3.  The  hymenium.     Using  a  prepared  slide,  state  the 
direction  of  its  cells  relative  to  the  surface  of  the 
gill.     Distinguish  in  it  two  kinds  of  cells,  (a)  club- 
shaped  ones,  paraphyses;  (b)  basidia  (sing.,  basid- 
ium),  ending  in  sterigmata  (sing.,  sterigma).    How 
many  sterigmata  terminate  each  basidium?     Ob- 
serve the  spores,  borne  on  the  basidia  and  hence 
called  basidiospores.     Are  the  basidiospores  all  of 
the    same   size?     Explain.     Describe   their   color, 
shape,  surface  markings  (if  any),  and  the  number  of 
cells  of  which  they  are  composed.     Is  the  color  of 
the  spores  constant?     To  what  is  the  color  of  the 
gills  due? 

4.  If  a  pileus  with  the  stipe  removed  is  placed  with 
the  gills  down  over  a  clean,  smooth  piece  of  paper 
(black  or  white  according  to  the  species  used) ,  then 
covered   with   a   tumbler   or  other  suitable  glass 
dish,  and  left  over  night,  a  print  of  the  spores,  as 
they  fell  from  the  gills,  will  be  found  on  the  paper 


AGARICUS   COMPESTRIS  I2Q 

in  the  morning.     Study  a  spore-print  of  this  species, 
describe  it  fully  and  state  how  it  was  formed. 

5.  Make  accurate  drawings  showing  all  features  ob- 
served under  E,  2  and  3. 

6.  Sexual  reproduction  is  unknown  among  the  fleshy 
fungi. 

7.  Diagram  the  life  history  of  the  species  studied. 

F.  Nutrition  and  Growth: 

1.  Could  the  mushroom  exist  independently  of  other 
plants?     Consider  this  question  thoughtfully  and 
answer  as  fully  as  possible  in  a  well-worded  para- 
graph. 

2.  Suggest  an  explanation  for  the  rapid  growth  of 
mushrooms. 

G.  General  Questions: 

1.  State  whether  there  is  a  division  of  physiological 
labor  in  this  plant,  and,  if  so,  to  what  extent. 

2.  In   what   ways   may   this   plant   become   widely 
distributed? 

3.  State,  with  reasons,  whether  you  consider  the  mush- 
room a  more  or  less  highly  developed  plant  than 
(a)  Spirogyra;  (b)  Polypodium. 


Puccinia  graminis  (WHEAT  RUST) 

A.  Classification: 

Division  I.     Thallophyta. 
Subdivision  B.    Fungi. 
Class  V.    Basidiomycetes. 
Series.    Protobasidiomycetes  (preliminary  group 

of  the  series). 
Order.    Uredinales. 
Family.    Uredinaceae. 
Genus.    Puccinia. 
Species,    graminis  Pers. 

B.  Habitat: 

1.  Examine  the  specimens  exhibited  in  the  laboratory, 
and  state  what  plants  are  infested  with  this  parasite, 
What  is   the    significance    of    its    specific    name 
(graminis)  ? 

2.  Puccinia  graminis  requires  two  different  kinds  of 
hosts  in  order  to  complete  its  life  history.     One  of 
these  is  the  barberry  (Berberis).    The  barberry- 
stage,  however,  is  not  absolutely  essential,  for  in 
certain  regions,  e.g.,  Australia,  the  Central  Western 
States,  and  California,  where  the  barberry  does  not 
naturally   grow,  this  stage  may  be  omitted,  the 
fungus  being  perhaps  carried  over  the  winter  season 
on  winter  wheat,   or  possibly   by   mycelium    in 
grain,  or  even  by  urediniospores. 


STAGE  (on  Berberis) 

C.  Naked-eye  Characters: 

i.  Study  the  infected  leaf  of  the  barberry.  On  its 
under  surface  observe  the  cluster-cups  or  aecia 
(sing.,  aecium). 

130 


PUCCINIA   GRAMINIS  131 

2.  On  the  upper  surface  observe  the  small  dots,  the 
pycnia  (pycnidia,  or   spermatia).    What   is   their 
color?    Their  shape?    What   relation  does  their 
position  bear  to  that  of  the  secia? 

3.  Study  both  aecia  and  pycnia  with  the  aid  of  a  hand 
lens.    Describe  carefully  the  appearance  of    the 
infected  areas. 

4.  Make  a  drawing,  life  size,  of  the  barberry  leaf,  show- 
ing the  features  under  C,  1-3. 

D.  Microscopic  Characters: 

1.  Study  longitudinal  sections  through    an    aecium, 
using  low  power. 

2.  How  are  the  infested  tissues  of  the  host  affected  by 
the  parasite? 

3.  Note  the  aeciospores.    Describe  their  shape.    Are 
they  all  of  the  same  shape  and  size?    How  are  they 
produced?    What  is  the  cause  of  the  cluster-cups 
that  appear  on  the  leaf-surface? 

4.  Make  out  all  you  can  of  the  details  of  the  mycelia, 
and  their  relation  to  the  cells  of  the  host-plant,  and 
describe. 

5.  Make  a  drawing  of  two  aecia  in  different  stages  of 
development,  one  before  the  epidermis  of  the  leaf 
has  been  ruptured.    Make    the  aecium    at  least 
30  mm.  in  longest  dimension. 

6.  Make  a  study,  similar  to  that  outlined  in  D,  1-5, 
of  the  pycnia,  as  seen  in  longitudinal  section.     Ob- 
serve the  slender  threads  and  the  minute  spermatia. 

7.  What  is  the  function  of  the  aeciospore?    Of  the 
pycnia? 

UREDO-STAGE  (on  Wheat,   Triticum  vulgare) 

E.  Naked-eye  Characters: 

i.  Study  the  diseased  spots  on  the  leaves  of  the  wheat. 


132  MORPHOLOGY  AND  LIFE  HISTORY 

Use  the  hand  lens,  if  necessary,  to  make  out  the 
features  clearly. 

2.  Is  the  shape  of  the  spots  (sori,  sing.,  sorus)  uniform 
and  characteristic? 

3.  State  their  color. 

F.  Microscopic  Characters: 

1.  Study  longitudinal  sections  through  a  uredo-sorus. 
If  the  material  is  not  fresh,  remove  some  of  the 
contents  of  the  sorus  with  a  needle,  and  mount  in 
water.     Study  under  high  power. 

2.  Describe  the  color,  shape,  and  relative  size  of  the 
cells.    Are  there  any  surface  marks?    Do  you  find 
any  remnants  of  the  pedicle  to  which  the  uredinio- 
spore  was  attached?    What  can  you  say  of  the 
thickness  of  the  cell- wall? 

3.  Of  how  many  cells  is  the  urediniospore  composed? 

4.  Make  careful  drawings  of  two  or  three  uredinio- 
spores,  at  least  15  mm.  in  longest  measure. 

5.  State  the  function  of  the  urediniospore. 

TELIAL  STAGE  (on  Wheat) 

G.  Naked-eye  Characters: 

i.  Study  the  telial  sori,  as  directed  under  E,  above. 

Describe  the  order  of  their  distribution. 
H.  Microscopic  Characters: 

1.  Study  as  directed  under  Ft  above. 

2.  Include  in  your  notes,  at  this  point,  a  description 
of  the  germination  of  the  teliospore  (teleutospore). 
What  is  its  function?     State  the  function  of  the 
basidium  (promycelium),  and  of  the  spring-sporete, 
or  basidiospores  (sporidia). 

I.   General  Questions: 

i.  What  features  seem  to  you  to  make  this  parasite 
easily  distributed,  and  difficult  to  eradicate? 


PUCCINIA   GRAMINIS  133 

2.  State,  with  reasons,  whether  you  would  consider 
Puccinia  graminis  higher  or  lower  in  the  scale  of 
life  than   Vaucheria   (or  Fucus),  and  Albugo   (or 
Mucor). 

3.  Write  a  brief  summary  of  the  life  history  of  Puccinia 
graminis,  and  devise  a  diagram  to  illustrate  this. 


NOTE 

From  the  fern  to  the  wheat  rust  we  have  studied  plants 
in  the  descending  order,  from  higher  to  lower  in  the  scale. 

We  now  return  to  the  ferns,  taking  the  quill-wort 
(Isoetes),  illustrating  the  Eusporangiatae. 

The  systematic  relationship  of  the  Isoetaceae  is  doubt- 
ful. On  the  basis  of  certain  structural  features  of  the 
gametophyte  (e.g.,  the  structure  of  the  archegonia,  and 
the  possession  of  multiciliate  sperms),  some  botanists 
class  them  with  the  Pteridophyta.  On  the  other  hand, 
some  features  of  the  anatomy  of  the  sporophyte  (e.g.,  the 
possession  of  a  ligule  on  the  sporophyll)  suggests  that 
they  are  more  closely  related  to  Selaginella  (Lepido- 
phyta). 


Isoetes  (QUILLWORT) 

A.  Classification: 

Division  III.    Pteridophyta. 
Class  I.     Eusporangiatae. 
Order.    Isoetales. 
Family.     Isoetaceae. 
Genus.    Isoetes. 
Species,     (e.g.,  lacustris.) 

B.  Habitat: 

Some  forms  grow  on  the  bottom  of  ponds,  others  in 
moist  meadows,  or  on  the  margins  of  bodies  of  water. 

THE  SPOROPHYTE 

C.  Naked-eye  Characters: 

1.  General  Features. 

(a)  Note  the  differentiation  of  the  plant  into  root 
and  shoot,  and  of  the  shoot  into  stem  and  leaf. 

(&)  Make  a  sketch,  natural  size,  showing  the 
general  appearance  of  the  entire  plant. 

2.  The  Stem: 

(a)  Without  removing  any  of  the  leaves  or  roots, 
ascertain  all  you  can  about  the  shape,  size, 
branching,  and  other  characters  of  the  stem, 
and  describe. 

(b)  With  a  sharp  scalpel,  make  a  cross-section  of 
the  stem  through  the  middle,  being  careful  not 
to  remove  any  of  the  leaves  or  roots. 

(c)  Describe  the  outline  of  the  stem  as  seen  in 
cross-section.    Note  the  longitudinal  furrows 
which  give  it  a  lobed  appearance. 

134 


ISOETES  135 

(d)  Are  the  roots  attached  to  any  special  region  of 
the  stem?    If  so,  describe. 

(e)  Study  the  cross-section,  identifying  the  central 
(vascular)  cylinder,  the  epidermal  layer,  and, 
between  the  two,  the  fleshy  tissue  composed  of 
several  regions   that  are   not   distinguishable 
to  the  naked  eye. 

(/)  Make  a  drawing  (X  3),  showing  the  outline  of 
the  stem  in  cross-section,  the  tissue-regions 
observed,  and  the  attachment  of  the  roots. 

3.  The  Roots. 

(a)  Describe  the  general  appearance  of  a  single  root. 
Does  it  taper?    Note  that  it  is  slightly  fleshy. 
Are  the  branches  forked  at  the  tip   (dicho- 
tomous),  or  lateral?    Dichotomous  branching 
of  roots  is  very  rare. 

(b)  Make  a  drawing  (X  2)  showing  these  features. 

4.  The  Leaves. 

(a)  Carefully  remove  one  of  the  outer  leaves  at  its 
point  of  attachment  to  the  stem,  first  noting 
carefully  which  is  its  inner  (ventral)  surface, 
and  which  is  its  outer  (dorsal)  surface. 

(b)  State  whether  the  leaf  is  sessile  or  petiolate. 
The  end  by  which  it  is  attached  is  the  leaf- 
base  and  the  remainder  of  the  leaf  is  called  the 
lamina   or   blade.    Note    that    the   blade   is 
subulate  (awl-shaped). 

(c)  Describe  the  exact  length  of  the  leaf  in  milli- 
meters.   Observe  the  slight  shallow  groove  or 
flattening.     On  which  side  of  the  leaf  is  it? 

(d)  Hold  the  leaf  up  to  the  light  and  observe  the 
single    vascular    bundle,    surrounded    by   air 
chambers    separated   into    compartments   by 
numerous  diaphragms. 


136  MORPHOLOGY  AND   LIFE   HISTORY 

(e)  Make  a  drawing  (X  2)  illustrating  the  features 
mentioned  in  4,  (c)  and  (d). 

(f)  Make  a  cross-section  of  the  blade  near  the 
middle,  and  note  the  number  of  air  chambers 
surrounding  the  vascular  bundle. 

(g)  Make  a  diagram,  10  mm.  in  diameter,  showing 
the  leaf-structure  in  cross-section. 

(/?)  On  plants  which  grow  under  water  no  stomata 
occur,  but  they  are  present  on  leaves  that  grow 
exposed  to  the  air.  Are  stomata  present  in 
your  specimen?  If  so,  make  a  drawing  of 
two  or  three,  each  15  mm.  in  longest  diameter. 

(i)  Study  carefully  the  expanded  base  of  this  leaf, 
noting  the  membranous  margins. 

(k)  Directly  above  the  leaf -insertion,  and  on  the 
ventral  (inner)  surface,  observe  the  cavity  or 
pit  (fovea),  containing  the  single  sporangium. 

(/)  Note  the  thin  membrane  (velum)  extending 
over  the  sporangium.  The  velum  is  formed  by 
the  projection  of  the  margin  of  the  fovea.  It  is 
absent  in  some  species,  and  in  /.  lacustris  it 
does  not  completely  cover  the  sporangium. 
In  terrestrial  species  there  is  no  opening  through 
it.  State  the  shape  and  location  of  this  open- 
ing in  your  specimen,  using  a  hand  lens  for  the 
observation. 

(m)  Above  the  fovea  find  a  flat,  membranous  out- 
growth, the  ligule.  Describe  its  shape  and 
state  toward  which  end  of  the  leaf  it  projects. 
The  slightly  swollen  base  of  the  ligule  is  in- 
serted in  a  depression  (foveola)  smaller  than  the 
fovea  and  directly  above  it.  This  last  point  is 
not  easily  made  out  except  with  the  aid  of  a 
hand  lens  or  microscope. 


ISOETES  137 

(n)  Make  drawings  as  follows: 

(1)  A  leaf -base,  20  mm.  at  greatest  breadth, 
showing    all    points    observed    under     4, 

(*')-«. 

(2)  A  diagram,  40  mm.  in  greatest  width,  of  an 
imaginary  cross-section,  of  the  sporophyll, 
taken  through  the  middle  of  the  fovea. 

(3)  A  diagram,  15  mm.  in  greatest  width,  of 
an  imaginary  median  longitudinal  section 
through  the  base  of  a  sporophyll. 

D.  Asexual  Reproduction: 

1.  Note  that  some  of  the  sporophylls  bear  large  spores 
(megaspores),  and  some  small  spores  (microspores) . 
Study   any  constant  differences  (a)  in  structure, 
(b)    in   position  on  the  stem,  between  the  mega- 
sporophylls  and  the  microsporophylls.     Define  each 
of  these  terms. 

2.  How  many  megaspores  does  a  megasporangium 
.    contain? 

3.  Measure  the  diameter  of  a  megaspore  in  millimeters. 
Study  and  describe  its  shape  under  the  low  power 
(mounted  in  water),   noting  any  surface  marks. 
Explain  the  presence  of  angles  on  the  spore. 

4.  Make  a  drawing  of  a  megaspore,  20  mm.  in  diameter. 
Indicate  the  amount  of  enlargement. 

5.  Study  microspores  under  high  power,  describing 
their  shape  and  surface  marks.     Draw  two  or  three 
to  the  same  scale  as  the  drawing  of  the  macro- 
spore.     The  number  of  microspores  in  I.  echinospora 
is  said  to  be  from  150,000  to  300,000;  of  megaspores 
150  to  300. 

6.  Why    is    Isoetes    a    heterosporus   pteridophyte  ? 
Compare    it    with    Polypodium    vulgare    in    this 
respect. 


138  MORPHOLOGY   AND   LIFE   HISTORY 

THE  GAMETOPHYTE 

The  germination  of  the  spores  and  the  development 
of  the  male  gametophyte  from  the  microspore,  and  of  the 
female  gametophyte  from  the  megaspore,  are  very 
difficult  to  follow,  and  will  be  omitted  here.  The  struc- 
tures of  the  gametophytes,  and  the  process  of  sexual  re- 
production should  be  carefully  studied  in  a  text-book, 
and  demonstrated  by  the  instructor,  if  material  is  available. 
E.  Nutrition  and  Growth: 

1.  Is  the  gametophyte  at  any  stage  dependent  upon 
the  sporophyte?    The  sporophyte  upon  the  game- 
tophyte?    (Consult  a  text-book.) 

2.  It  is  important  to  remember  that: 

(a)  The  microspore  begins  to  germinate  before  it  is 
set  free,  dividing  into  two  cells,  a  large  one  and 
a  small  one.    The  smaller  cell  constitutes  the 
entire  vegetative  portion  of  the  male  gameto- 
phyte.   The  larger  cell  develops  into  an  an- 
theridium,  consisting  of  four  wall-cells,  and  four 
central  cells.     Each  of  the  latter  develops  into 
a  multiciliate,  spirally  coiled  sperm,  resembling 
those  of  the  true  ferns. 

(b)  The  megaspore  begins  to  germinate  after  it  is  set 
free.    It    never    develops    chlorophyll-bearing 
tissues.     In  germination   the  nucleus  divides 
into  about  50  nuclei  before  any  cells  are  formed. 
Then  cells   begin  to  be  organized  about  the 
nuclei,  forming  a  small-celled  tissue  in  the  apex 
of  the  spore  (where  the  three  ridges  meet), 
and  a  larger-celled  tissue  below.    Archegonia 
then  develop  in  the  small-celled  tissue,  and  the 
larger-celled  tissue  serves  to  nourish  the  young 


ISOETES  139 

embryo-sporophyte,    that   develops   from   the 
fertilized  egg. 

The  archegonia  are  exposed  for  fertilization 
by  the  splitting  of  the  wall  of  the  megaspore 
along  the  ridges,  but  the  prothallus  itself  does 
not  project  beyond  the  walls  of  the  spore. 

When  the  sporophyte  begins  to  develop  from 
the  fertilized  egg,  it  continues  to  grow,  without 
any  resting  period,  until  it  is  mature. 
Diagram  the  life  cycle  of  Isoetes,  as  directed  for 
Marchantia.    Let  MG  =  male  gametophyte;  FG  = 
female    gametophyte;   5  =  sperm;    e  =  egg;   S  = 
sporophyte;  mi  =  microspore;  mg  =  megaspore. 


Equisetum  (HORSETAIL) 

A.  Classification: 

Division  IV.     Calamophyta. 
Class  II.     Equisetineae. 
Order.     Equisetales. 
Family.     Equisetaceae. 
Genus.     Equisetum. 
Species,     (e.g.)  arvense. 

B.  Habitat: 

i.  The  field  horsetail  (E.  arvense),  is  common  along 
railway  embankments,  roadsides  and  fields.  It 
apparently  prefers  north-facing  slopes,  and  has  a 
great  tendency  to  become  weedy. 

C.  Naked-eye  Characters: 
i.  The  Stem. 

(a)  Using  herbarium  specimens  or  alcoholic  material, 
if  fresh  material  is  not  available,  observe  the 
underground  stem  (rhizome),  and  the  upright 
aerial  branches. 

(b)  Of  the  latter,  observe  two  kinds;  (i)  non-green, 
unbranched,    bearing   only   scale   leaves,    and 
terminating  in  a  prominent  strobilus  or  cone; 
(2)  green  and  branched,  bearing  leaves,  but 
no  cone. 

(c)  Which  kind  of  aerial  branch  appears  first  above 
ground  in  the  spring  ?    What  advantage  may  this 
possess  for  the  species? 

(d)  Explain  the  physiological  significance  of  the 
green  color  of  the  non-reproductive  branches. 

140 


EQUISETUM  141 

Of  what  significance,  in  this  connection,  is  their 
profuse  branching? 

(e)  Describe  the  surface  of  the  stem  along  the 
internodes,  noting  the  presence  or  absence  of 
ridges,  the  hardness  (or  otherwise),  and  the 
"feel"  of  the  surface.  To  what  are  the  last 
two  characters  due? 

(/)  If  material  of  Equisetum  hyemale  (the  "scour- 
ing rush")  is  available,  it  will  be  instructive  to 
burn  a  portion  of  the  stem  in  a  Bunsen  flame, 
and  to  examine  the  unburned  portion  under 
a  microscope.  The  preservation  of  the  cell- 
walls,  uninjured  by  the  flame,  is  due  to  the 
fact  that  they  are  impregnated  with  silica, 
taken  up  by  the  plant  from  the  soil  in  the 
form  of  a  silicate,  and  secreted  by  the  proto- 
plasm of  each  individual  cell.  It  is  the  pres- 
ence of  the  silica  that  made  this  species  useful 
for  scouring  cooking  utensils,  and  thus  gave  it 
its  common  name. 

2.  The  Leaves. 

(a)  Describe  the  shape  and  character  of  the  leaves; 
their  arrangement  on  the  stem  (i.e.,  opposite, 
alternate,  or  whorled). 

(b)  Do  the  leaves  function  in  the  work  of  photo- 
synthesis?   In  what  organ  or  organs  is  that 
function  performed? 

(c)  To  what,  in  the  fern,  are  the  branches  of  the 
vegetative  part  of  the  stem  analogous?    To 
what  are  they  homologous?    To  what,  in  the 
fern,  are  the  scales  at  the  nodes  analogous? 
To  what  are  they  homologous?    Explain. 

3.  The  Roots. 

(a)  Briefly  describe  their  character  and  distribu- 


142  MORPHOLOGY  AND   LIFE   HISTORY 

tion.     Does  their  distribution  on  the  rhizome 
bear  any  constant  relation  to  the  point  of  origin 
of  the  aerial  branches? 
4.  Make  drawings  showing  all  points  observed  under 

c,  1-3. 

D.  Asexual  Reproduction: 

1.  Vegetative  Propagation. 

(a)  Describe  the  possibility  of  the  multiplication 
of  new  individuals  by  isolating  pieces  of  the 
rhizome. 

2.  Reproduction  by  Spores. 

(a)  Sketch  the  strobilus  or  cone  (X  3). 

(b)  Make  a  cross-section  of  the  cone  at  about  one- 
third  of  the  distance  from  the  apex,  and  observe 
the  central  axis,  and  the  manner  in  which  the 
sporophylls  are  borne. 

(c)  Carefully  dissect  off  a  sporophyll,  and  observe 
(i)  its  stalk;  (2)  its  peltate  (shield-like)  top; 
(3)  hanging  from   the  under   surface   of   the 
shield,  the  sporangia.    How  many  sporangia 
on  each  sporophyll?    Examine  several  sporo- 
phylls to  see  if  the  number  of  sporangia  is 
constant.    Describe    the    dehiscence    of    the 
sporangia. 

(d)  Examine    the    spores   under    the   microscope. 
Can   you  detect  more  than  one  size;  i.e.,  is 
Equisetum   a   homosporus   or   a   heterosporus 
plant? 

(e)  Describe    the  appendages    (elaters),    of    the 
spores.     How  many  on  each  spore?    They  are 
formed  by  a  modification  of  the  outer  coat  of 
the    spore.     Observe     their    behavior    when 
breathed  on  at  frequent  intervals. 

(/)  While  the  spores  are  morphologically  homo- 


EQUISETUM  143 

sporous,  they  give  rise  to  dioecious  gameto- 
phytes.  Are  they,  therefore,  physiologically 
alike? 

(g)  Since  the  spores  have  different  sex-value,  some 
giving  rise  to  antheridial,  others  to  archegonial 
prothallia,  suggest  the  advantage  of  the  hygro- 
scopic elaters  in  tending  to  tangle  up  together 
several  spores  before  they  germinate. 

(h)  Make  drawings  illustrating  all  points  observed 
under  Z),  2,  (a)-(/). 

E.  Sexual  Reproduction: 

1.  It  is  not  essential,  in  an  introductory  course  to 
study  the  gametophytes,  and  sexual  reproduction 
of  Equisetum,  and  it  is  seldom  possible  to  secure 
suitable  material  in  sufficient  quantity  for  a  large 
class. 

2.  If  material  is  abundant  and  time  permits,   the 
gametophytes    may    be    studied,    described,    and 
sketched,  noting  especially  color  and  general  form, 
branching,   rhizoids,   archegonia,   antheridia,   and 
the  dioecious  habit. 

3.  From  prepared  slides  further  details  as  to  arche- 
gonia, antheridia,  eggs,   sperms,   and  fertilization 
may  be  studied,  under  the  instructor's  direction. 

F.  Division  of  Physiological  Labor: 

i.  Write  two  or  three  paragraphs  describing  the 
•  division  of  physiological  labor,  (a)  as  between 
various  vegetative  processes,  and  (b)  between  the 
latter  and  reproductive  processes.  Give  special 
attention  in  this  to  the  work  of  each  of  the  three 
kinds  of  branches. 

G.  Life  Cycle: 

i.  Make  a  diagram,  as  previously  for  other  forms, 
illustrating  the  life  cycle  of  Equisetum. 


Lycopodium  (CLUB-MOSS) 

A.  Classification: 

Division  V.    Lepidophyta. 
Class  I.    Lycopodineae. 
Order.    Lycopodiales. 
Family.    Lycopodiaceae. 
Genus.    Lycopodium. 
Species,     (e.g.,  clavatum.) 

B.  Habitat: 

i.  Nearly  all  the  species  of  Lycopodium  prefer  moist 
situations,  and  one  or  two  of  them  are  aquatic. 
They  are  widely  distributed  over  the  earth,  in  both 
hemispheres,  from  the  torrid  to  the  frigid  zones, 
and  commonly  grow  in  shady  or  partly  shaded 
places.  Lycopodium  Selago  and  a  few  other  species 
are  epiphytic.  They  all  prefer  a  substratum  rich 
in  humus  or  other  organic  matter. 

THE   SPOROPHYTE 

C.  Naked-eye  Characters: 

1.  General  Features. 

(a)  Note  whether,  or  not,  the  plant  is  differentiated 
into  root  and  shoot,  and  the  latter  into  stem 
and  leaves.  If  the  stem  branches,  briefly 
describe. 

2.  The  Stem. 

(a)  Describe  the  attitude  of  the  stem  (e.g.,  erect, 
trailing).  Does  the  tip  of  the  stem  turn  up, 
or  otherwise? 

144 


LYCOPODIUM  145 

(b)  Describe  the  mode  of  blanching. 

(c)  Are  there  any  specialized  (e.g.,  cone-bearing) 
branches? 

(d)  Is  there  a  terminal  bud?    Lateral,  or  axillary 
buds? 

3.  The  Roots. 

(a)  Does  the  stem  bear  roots  only  at  its  posterior 
end,  or  otherwise?     Describe.   . 

(b)  Briefly  characterize  the  roots. 

4.  The  Leaves. 

(a)  State  their  manner  of  distribution  on  the  stem. 

(b)  Describe  an  individual  leaf. 

5.  Make  drawings  as  follows:  (i)  of  a  portion  of  the 
stem,  to  show  mode  of  branching,  distribution  of 
leaves  and  roots,  and  other  general  features,  natural 
size;  (2)  a  leaf  (X  5). 

D.  Asexual  Reproduction: 

1.  Vegetative  Propagation. 

(a)  Describe  the  method  of  propagation  by  the 
annual  apical  growth  of  the  stem. 

(b)  Does    the   species   you   are   studying   in    the 
laboratory  possess  buds  or  bulbils  that  may 
fall  away,  and  develop  into  new  plants?     If  so, 
describe  their  distribution  on  the  stem;  their 
relation  to  leaves,  etc. 

2.  Reproduction  by  Spores. 

(a)  Describe  the  location  of  sporangia,  especially 
their  relation  to  leaves.    Are  they  borne  in  the 
leaf -axils  or  on  the  leaf -surf  ace?    If  the  latter, 
on  which  surface?    What  relation  do  they  bear 
to   the   leaf -base?    Is    there   more   than   one 
sporangium  to  each  leaf? 

(b)  Are  there  special  sporophylls?     If  so,  how  do 

they    differ    in    location    and   characteristics 
10 


146  MORPHOLOGY  AND   LIFE  HISTORY 

from  the  foliage-leaves?  Are  they  aggregated 
in  a  cone?  If  so,  what  effect  does  the  forma- 
tion of  the  cone  have  on  the  further  growth  of 
the  branch? 

(c)  Is  Lycopodium  a  homosporus  or  a  heterosporus 
plant? 

(d)  Describe   a   single   sporangium,   its   mode   of 
dehiscence,    and    the    relative    number    (i.e., 
few  or  many)  of  spores  it  bears. 

(e)  Into  what  do  the  spores  develop? 

(/)  Make  drawings  as  follows:  (i)  a  cone  (X  4); 
(2)  a  sporophyll,  with  sporangium  (X  10);  (3) 
under  the  low  power  a  few  of  the  spores,  and 
(from  younger  sporangia)  a  few  of  the  spore- 
tetrads. 

THE   GAMETOPHYTE 

E.  Sexual  Reproduction: 

1.  The  gametophyte  of  Lycopodium  is  rarely  seen,  and 
not    readily    obtained    in    artificial    culture.     Its 
laboratory  study  may  be  omitted  in  a  beginning 
course,  but  the  subject  should  be  presented  by 
lecture,  or  preferably  studied  from  a  text  and  then 
discussed  in  class,  with  demonstrations  of  preserved 
material. 

2.  Diagram  the  life  cycle  of  Lycopodium. 


Selaginella  (LITTLE  CLUB-MOSS) 

A.  Classification: 

Division  V.    Lepidophyta. 
Class  II.    Lepidodendrineae. 
Order.     Selaginellales. 
Family.     Selaginellaceae. 
Genus.     Selaginella. 

Species,    sp.    (Any  available  species  may 
be  used.) 

B.  Habitat: 

:.  Various  species  of  Selaginella  are  common  in  cul- 
tivation in  greenhouses.  In  nature  they  usually 
grow  in  moist  situations,  usually  preferring  shade. 

THE   SPOROPHYTE 

C.  Naked-eye  Characters: 

1.  General  Features. 

(a)  If  possible,  observe  plants  of  various  species 
growing  in  greenhouses,  noting  their  general 
appearance  and  habit  (e.g.,  erect,  climbing, 
trailing). 

2.  The  Stem. 

(a)  By  breaking  off  a  small  piece  from  the  end  of 
your  specimen,  ascertain  whether  the  stem  is 
tough,  brittle,  fibrous,  etc. 

(b)  Describe  the  mode  of  branching  (e.g.,  alternate, 
opposite,  dichotomous  (forked),  etc.).    Do  the 
branches  bear  any  relation  to  the  leaves,  e.g., 
are  they  in  leaf-axils? 

147 


148  MORPHOLOGY  AND  LIFE   HISTORY 

(c)  Is  the  branch  differentiated  into  regions?    If 
so,  briefly  describe. 

(d)  Does  the  branch  show  a  tendency  to  be  dorso- 
ventral?    How  do  you  determine  this? 

(e)  Do  you  note,  in  entire  plants,  any  indications 
of  response  to  gravity,  moisture,  or  the  direction 
of  light? 

2.  The  Leaves. 

(a)  Describe  their  position  on  the  stem.     Is  the 
flat  appearance  of  the  stem  due  to  the  leaves 
being  opposite,  or  to  the  attitude  they  have 
assumed  as  they  mature. 

(b)  Are  the  leaves  differentiated  into  petiole,  blade, 
etc.? 

(c)  Describe  any  apparent  adjustment  or  arrange- 
ment resulting  in  the  most  favorable  illumina- 
tion of  leaves. 

(d)  Describe  any  variations  in  the  color  of  the 
leaves,  and  endeavor  to  account  for  it. 

3.  The  Roots. 

(a)  Is  the  plant  rooted  in  the  soil? 

(b)  Do  the  roots  branch?    If  so,  describe. 

(c)  Are  there  any  other  roots  besides  those  in  the 
soil?    If  so,  describe  them,  and  their  location, 
and  suggest  any  advantage  they  may  be  to  the 
plant. 

(d)  Make    drawings    to    illustrate    all    characters 
observed,  including  (i)  a  portion  of  the  leafy 
branch  (X  2) ;  (2)  a  leaf  (X  10) ;  (3)  aerial  roots, 
if  any. 

D.  Microscopic  Characters: 
i.  The  Leaf. 

(a)  Mount  an  entire  foliage-leaf  in  water  or  clear- 
ing fluid  on  a  slide.    Observe  under  the  micro- 


SELAGINELLA  149 

scope,  using  low  and  high  powers,  and  describe 
all  details  of  leaf-structure  thus  brought  out, 
including 

(b)  The  shape  and  arrangement  of  the  cells;  the 
color,  size,  and  distribution  of  the  plastids  in 
the  cells;  any  other  cell  contents; 

(c)  Variations  between  marginal  cells,  those  along 
the   central   axis,    and    those   lying   between. 
Account  for  any  constant  differences  observed. 
Do  you  think  any  observed  differences  may  be 
attributed  to  environment?    Explain. 

(d)  Can  you  identify  a  tiny,   membranous  flap, 
the  ligule,  near  the  leaf -base?    On  which  side 
of  the  leaf  (dorsal  or  ventral)  is  it?    Be  sure 
to  examine  both  sides  of  the  leaf  in  this  connection. 

(e)  Are    there    stomata?      If    so,    describe    their 
location. 

(/")  Make  drawings  sufficiently  large  to  illustrate 

all  points  observed  under  D. 
2.  The  Stem. 

(a)  With  the  razor,  make  thin  cross-sections  of 
the  stem,  and  mount  them  in  water  or  clearing 
fluid. 

(b)  Is  the  stem  differentiated  into  (i)  epidermis; 
(2)   vascular  regions;  (3)   fundamental  tissue 
(cortex)?    If  so,  describe. 

(c)  Note  the  presence  or  absence  of  air-spaces. 

(d)  Compare  the  tissue-system  of  the  Selaginella 
(  stem  with  those  in  the  fern. 

(e)  Describe  the  distribution  of  xylem  and  phloem 
in  the  vascular  bundle. 

(/)  Do  you  find  indications  of  vascular  bundles 
passing  out  to  the  leaves? 


150  MORPHOLOGY  AND   LIFE   HISTORY 

(g)  Draw  a  section  of  the  stem  (X  20),  to  illustrate 

2,  (oM«). 
E.  Asexual  Reproduction: 

1.  Vegetative  Propagation. 

(a)  Describe  any  means  of  vegetative  propagation 
disclosed  by  your  observations,  already  made. 

(b)  If  opportunity  offers,  the  vegetative  propaga- 
tion  of    Selaginella    may    be   experimentally 
demonstrated  in  the  greenhouse  or  Wardian 
case. 

2.  Reproduction  by  Spores. 

(a)  Observe    the    "cones."    How    are    they    dis- 
tinguished?   Are  they  terminal  on  the  main 
branches,  or  axillary? 

(b)  Draw  (X  5). 

(c)  Place  a  small  portion  of  a  branch,  bearing  several 
mature  cones,  under  a  glass  bell- jar,  and  after 
twenty-four  to  forty-eight  hours  observe  the 
distance  to  which  the  spores  have  been  projected. 
Note  the  two  kinds,  their  relative  number,  and 
differences  in  color,  etc. 

((/)  Carefully  remove  sporophylls  (i)  from  near  the 
base  of  the  cone;  (2)  from  the  middle  or  above, 
and  mount  in  water  or  clearing  fluid,  keeping 
distinct,  on  separate  slides,  those  from  the  two 
regions. 

(e)  Note  both  megasporophylls,  bearing  mega- 
sporangia,  and  microsporophylls  bearing  micro- 
sporangia.  How  are  they  distinguished? 

(/)  Are  the  sporangia  inserted  on  the  leaf,  or  on 
the  stem  in  the  axil  of  the  leaf?  Compare  with 
the  other  plants  studied  in  this  respect* 

(g)  Describe  the  structure  of  the  walls  of  the 
sporangia. 


SELAGINELLA  151 

(ft)  Carefully  count  and  record  the  number  of 
megaspores  in  one  megasporangium.  Is  the 
number  always  even? 

(i)  Carefully  observe  the  megaspores  under  a  high 
power,  and  endeavor  to  account  for  their  shape. 

(;)  Make  drawings  to  show  all  points  observed 
under  £,  2,  (a)-(h). 

(k)  Make  a  study  of  the  microsporophylls,  micro- 
sporangia,  and  microspores,  similar  to  those 
just  made  under  E,  2,  (a)-(i). 

(/)  The  number  of  microscopes  is  too  large  to 
permit  of  their  being  readily  counted.  Sug- 
gest any  advantage  to  the  plant  in  such  a  large 
number  of  microspores.  Explain  the  cause  of 
the  difference  in  size.  Suggest  an  advantage 
to  the  plant  in  the  large  size  of  the  megaspore. 
(m)  Mount  megaspores  and  microspores  together 
and  make  drawings  to  show  their  relative 
sizes. 

(n)  Make  drawings  to  illustrate  all  points  observed 
under  E,  2,  (k). 

F.  Sexual  Reproduction: 

i.  The  gametophytes  of  Selaginella  are  not  readily 
obtained  in  suitable  form  for  study.  If  prepared 
slides  are  available,  studies  may  be  made  of: 

(a)  Archegonia  and  eggs. 

(b)  Antheridia  and  sperms. 

G.  Comparisons: 

1.  Compare  the  relative  prominence  of  the  gameto- 
phyte  and  sporophyte  in  Selaginella.    Compare, 
in  this  respect  with  all  the  forms  previously  studied. 

2.  Compare  the  method  of  reproduction  by  spores  in 
Selaginella    with    that    in   the    forms  previously 
studied.     Why  should  Selaginella   be  considered 


152  MORPHOLOGY  AND   LIFE   HISTORY 

either   higher  or   lower  in   the  scale  of  life  than 
those  forms? 
H.  Life  Cycle: 

i.  Make  a  diagram  to  illustrate  the  life  cycle  of 
Selaginella.  Briefly  state  differences  between  this 
life  history  and  that  of  the  fern,  and  of  Anthoceros. 


Zamia  floridana  (A  CYCAD) 

A.  Classification: 

Division  VI.     Cycadophyta  (The  Cycads). 
Class  II.     Cycadineae  (Modern  Cycads). 
Order.     Cycadales. 
Family.     Cycadaceae.1 
Genus.    Zamia. 
Species,    floridana. 

B.  Habitat: 

i.  Most  of  the  Cycadales  occur  only  within  the  tropics, 
but  two  genera,  Zamia  and  Cycas,  are  subtropical. 
Zamia  occurs  in  the  United  States  only  in  Florida, 
'where  it  is  rather  common.  It  is  frequently  culti- 
vated in  greenhouses. 

VEGETATIVE   ORGANS 

C.  The  Stem: 

i.  Briefly  describe  the  stem,  noting  its  general  appear- 
ance, size,  relation  between  its  diameter  and  height, 
variations  in  diameter,  character  of  the  surface,  its 
relation  to  the  surface  of  the  soil.  Note  the  pres- 
ence or  absence  of  branches. 

D.  The  Leaves: 

i.  Describe  their  arrangement  on  the  stem,  the  nature 
of  the  blade  (entire,  divided,  etc.),  the  color,  and 

1  By  some  botanists  the  genera  Zamia,  Macrozamia,  and  Dioon,  having 
both  staminate  and  carpellate  cones,  are  assigned  to  a  separate  family 
(Zamiaceae),  distinguished  from  the  Cycadaceae  (in  the  narrower  sense), 
which  bear  only  the  microsphorophylls  in  cones. 

153 


154  MORPHOLOGY   AND   LIFE   HISTORY 

the  presence  or  absence  of  a  petiole.  Describe 
accurately  the  vernation  (condition  in  the  bud),  as 
shown  by  young  leaves  just  unfolding. 

2.  Suggest  any  advantage  to  the  plant  of  any  of  the 
facts  recorded  under  D,  i. 

3.  Compare  the  character  of  the  leaves  with  that  of 
any  of  the  ferns. 

E.  The  Roots: 

i.  Briefly  state  their  location  and  functions. 

REPRODUCTIVE   ORGANS 

F.  The  Staminate  Cones: 

1.  Describe  their  appearance,  and,  if  the  material  is 
suitable,  their  distribution  on  the  plant. 

2.  Describe,  accurately,  the  distribution  of  the  micro- 
sporophylls  (stamens)  on  the  main  axis,  or  stem,  of 
the  cone. 

3.  Make  drawings,  natural  size,  showing  (a)  a  surface 
view  of  the  cone;  (b)  the  cone  as  seen  in  longitudinal 
section? 

4.  Remove  one  of  the  stamens.     Describe  it,  and  note 
the  microsporangia  (pollen-sacs)  attached  to  its 
lower  surface.     Describe  them,  their  number,  dis- 
tribution,  mode   of  attachment,   and  manner   of 
opening  (dehiscence) . 

5.  Make  drawings  (a)  of  a  stamen  with  pollen-sacs 
attached;  (b)  of  two  or  three  pollen-sacs  (X  10). 

6.  The  staminate  cone  is  in  reality  a  primitive  flower. 
From  this  study,  of  what  structure  would  you  infer 
that  flowers  are  a  modification? 

G.  The  Male  Gametophyte: 

i.  The   young  pollen-grain    (microspore)    begins   to 
germinate  before  it  leaves  the  pollen-sac,  two  divi- 


ZAMIA   FLORID  ANA  1 55 

sions  of  its  nucleus  taking  place.  By  the  first  cell- 
division  two  cells  are  formed,  one,  the  first  prothal- 
Hal  cell,  representing  the  vegetative  portion  of  the 
male  prothallus;  the  second,  or  antheridial  cell 
(called  the  "antheridial  initial"  by  some  botanists), 
divides  again,  forming  a  tube-cell  and  a  generative 
cell.  By  the  division  of  the  generative  cell,  the 
stalk-cell  and  body-cell  are  formed.  The  division 
of  the  body-cell  gives  rise  to  two  sperm-mother- 
cells,  and  each  of  these  latter  become  transformed 
into  a  motile  sperm. 

Complete  the  following  diagram  of  the  above  se- 
quence of  cell-divisions: 

Microspore 
O 


First  Proth.    °  °     Anth.  Cell 

Cell 

3.  Mount  several  pollen-grains  in  water,  and  examine 
them  under  the  high  power.     Describe  their  shape 
and  contents.     Draw. 

4.  The  study  of  the  mature  male  prothallus,  produced 
by  the  formation  of  a  pollen-tube,  will  be  omitted 
here. 

H.  The  Young  Carpellate  Cone: 

1.  The  youngest  cones  offered  for  study  were  collected 
about  March  i. 

2.  Describe  the  cone,  and  the  distribution  of  the  mega- 
sporophylls   (carpels)  on  its  main  axis,  or  stem. 
Draw,  natural  size. 

3.  Carefully  dissect1  off  one  of  the  carpels.    Describe 

1  For  economy  of  material,  with  large  classes,  excised  carpels  may  be 
supplied. 


156  MORPHOLOGY  AND   LIFE   HISTORY 

its  form  and  surface  characters,  and  note  the  num- 
ber, and  place  and  mode  of  attachment  of  the  large 
megasporangia  (ovules) .    Note  their  color.     Draw, 
natural  size. 
4.  Do  you  find  smaller,  undeveloped  ovules?     These 

have  probably  not  been  pollinated. 
/.  The  Young <  Ovule: 

1.  Is  the  ovule  enclosed  by  the  carpel,  or  is  it  naked? 
State  why  Zamia  is  classed  as  a  gymnosperm. 

2.  At  the  end  of  the  ovule,  opposite  its  point  of  attach- 
ment, note  the  small,  often  slightly  elevated,  dark 
spot,  which  marks  the  place  of  the  micropyle  (small 
gateway),  through  which  the  pollen-grain  passes 
in  order  to  reach  the  pollen-chamber  within.     This 
process  is  called  pollination.     In  Zamia,  pollination 
occurs  about  Jan.  i. 

3.  Remove  an  ovule,  carefully  noting  where  and  how 
it  is  attached  to  the  carpel.     -M 

4.  Describe  its  surface  and   shape.    How  may   the 
latter,  in   part,   be   accounted   for?    At  the  end 
opposite  the  micropyle  observe  the  scar  (hilum), 
where  the  ovule  was  attached.     Draw.1 

5.  With  the  scalpel,  make  a  slight  longitudinal  incision 
of  the  integument  (wall)  of  the  ovule,  being  careful 
not  to  cut  too  deeply,  so  as  to  injure  the  delicate 
structures  within.    Describe  the  character  of  the 
tissue  of  the  integument. 

6.  The   tissue   next  within   the   integument  is   the 
nucellus,   or  megasporangium.     The  integuments 
are  outgrowths  of  the  nucellus. 

1  Arrange  all  the  drawings,  showing  the  ovule  at  different  ages,  serially, 
on  a  new  sheet  of  drawing  paper,  so  as  to  facilitate  the  comparison  of  the 
different  stages,  and  to  show  at  a  glance  the  changes  which  the  different 
parts  undergo. 


ZAMIA  FLORID  ANA  157 

7.  After  making  a  longitudinal  incision,  very  carefully 
remove  the  nucellus,  noting  the  greater  thickness  of 
the  tissue  at  the  micropylar  end.    This  tissue  serves 
as  nourishment  for  the  germinating  pollen-grain. 

8.  Within  the  nucellus  is  the  globular  young  female 
gametophyte,  or  endosperm.    Describe  and  (from 
your  reading  in  the   text-book)    account  for  its 
consistency. 

9.  With  the  razor  make  a  median,  longitudinal  section 
of  the  entire  ovule.     Study  and  draw,  naming  all 
the  parts. 

/.  Older  Stages  in  the  Development  of  the  Ovule: 

1.  Examine  ovules  collected  about  April  i,  as  directed 
under  /.     Compare  their  size  with  that  of  the 
younger  ovules.     Observe  the  fleshy  texture  being 
assumed  by  the  outer  portion  of  the  tissue  of  the 
integument,  and  the  differentiation  of  a  harder 
inner  layer  (endopleura) . 

2.  Describe  the  changes  which  the  nucellus  has  under- 
gone.    Account  for  these  changes.     (The  appear- 
ance of  the  nucellar  tissue  may  be  due,  in  part,  to 
its  disintegration  by  the  growing  pollen- tubes.) 

3.  Remove  the  nucellus  and  describe  the  appearance 
of  the  endosperm.    Note  the  slight  depression  in 
its  micropylar  end.    What  change  has  taken  place 
in  its  consistency?    Account  for  the  change. 

4.  With  a  scalpel  cut  away  the  endopleura,  and  then, 
with  a  razor,  make  a  clean,  median  longitudinal 
section  of  the  endosperm,  and  observe,  imbedded 
in  its  micropylar  end.   two  or  more  archegonia. 
These  open  into  the  depression  mentioned  above  by 
a  short  neck,  composed  of  only  two  cells.    The  short 
neck-canal  may  be  seen  if  the  section  passes  through 
a  suitable  plane. 


158  MORPHOLOGY  AND  LIFE   HISTORY 

5.  With  a  hand  lens  observe  the  wall  of  the  arche- 
gonium,  and  within,  filling  the  venter,  the  large 
ovum,  or  egg. 

6.  As  outlined  above  (/,  1-4),  examine  and  describe 
an  ovule  one  month  older  (about  May  i),  carefully 
noting  the  changes  which  the  different  parts  have 
undergone.    Observe  especially  the  development 
of  the  hard  inner  layer  of  the  integument.     May 
this  feature  be  of  any  advantage  to  the  plant? 
If  so,  how?    Does  any  of  the  nucellus  remain? 
If  so,  describe.    Note,  in  the  depression  of  the  endo- 
sperm, the  openings  into  the  archegonia.    How  many 
are  there?    Draw  this  depression  as  seen  in  end 
view. 

7.  Construct  a  diagram  of  an  ovule  of  this  age  as  seen 
in  median  longitudinal  section,  carefully  labeling 
all  parts. 

8.  Make  a  diagrammatic  drawing  of  a  cross-section  of 
the  same  ovule  passing  through  the  venters  of  the 
archegonia. 

9.  In  ovules  one  month  older  (about  June  i)  the  sac- 
like  proembryo  may  be  seen,  lining  the  walls  of  the 
venter  of  the  archegonium,  and,  growing  from  its 
basal  end  into  the  tissue  of  the  endosperm,  the 
prominent  suspensor,  at  the  free  end  of  which  the 
embryo  begins  to  develop.    As  the  suspensor  and 
embryo  increase  in  size,  a  cavity  is  formed  in  the 
surrounding  endosperm.    This  cavity  results  from 
the  digestion  of  the  endosperm  tissue^  which  goes 
to  nourish  the  growing  embryo  and    suspensor. 
Suggest  how  this  digestion  and  subsequent  nutri- 
tion may  be  accomplished. 

10.  Make  a  drawing  of  a  median  longitudinal  section 
of  the  ovule  at  this  stage. 


ZAMIA  FLORID  ANA  159 

K.  The  Seed: 

1.  The  seed  matures  about  July  i.     Study  the  struc- 
ture of  a  ripe  seed,  comparing  it  in  every  point  with 
the  structure  of  the  unripe  ovule,  as  directed  above 

(J,  i-™). 

2.  Note   the   soft,   outer   layer   of   the   integument. 

Describe  it. 

3.  In  cutting  away  the  hard,  shell-like  inner  layer 
(endopleura)  be  careful  not  to  disturb  the  portion 
of  the  nucellus  that  fits  like  a  cap  over  the  mycro- 
pylar  end  of  the  endosperm.    Now  carefully  lift 
this  portion  of  the  nucellus  and  observe  the  long, 
coiled  suspensor  attached  to  it,  and  (at  its  other 
end)  to  the  projecting  thick,  round  peg  (hypocotyl) 
of  the  embryo. 

4.  With  the  scalpel  gradually  remove  one-half  of  the 
endosperm,  until  you  expose  the  embryo  (young 
sporophyte)  imbedded  in  it.    Is  the  embryo  curved 
or  straight?    Is  it  now  confined  to  the  venter  of 
the  archegonium? 

5.  Observe  that  the  hypocotyl  bears  fleshy  seed-leaves 
(cotyledons).    How   many   are   there?    Compare 
their  lengths. 

6.  Does  more  than  one  embryo  come  to  maturity  in 
any  one  seed? 

7.  When  the  sporophyte  of  Zamia  begins  to  develop, 
is  its  growth  continuous  to  maturity,  or  does  a 
period   of   rest  intervene   between   two  stages  of 
growth?     Compare  Zamia  with  the  fern,  moss,  and 
Selaginella  in  this  respect. 

8.  Define  a  seed,  and  state  how  it  differs  from  an 
unripe  ovule,  and  from  a  spore. 

9.  Suggest  any  advantage  to  the  plant  of  the  seed- 
habit. 


l6o  MORPHOLOGY  AND   LIFE  HISTORY 

L.  Nutrition: 

1.  Describe  the  relative  ability  of  the  mature  sporo- 
phyte  and  the  gametophyte  to  lead  an  independent 
existence.     Is  the  gametophyte  ever  independent 
of  the  sporophyte?    Does  the  sporophyte  ever  live 
parasitically  on  the  gametophyte? 

2.  Why  does  the  embryo-sporophyte  need  a  supply  of 
food  stored  in  the  seed? 

3.  Would  it  be  of  any  special  advantage  to  Zamia  to 
have  a  well-developed  male  gametophyte?    Why? 

4.  At  home  write  a  detailed  description  of  the  changes 
undergone  by  a  starch  grain,  formed  in  the  leaf  of 
a  mature  carpellate  sporophyte,  until  it  becomes 
part  of  the  tissue  of  the  embryo-sporophyte  of  the 
next  sporophyte-generation. 

5.  Make  a  diagrammatic  outline  (using  words,   not 
drawings)  showing  the  life  cycle  of  Zamia  from 
sporophyte  to  sporophyte. 


Pinus  laricio  (AUSTRIAN  PINE) 

A.  Classification: 

Division  VI.     Spermatophyta. 
Subdivision  A.     Gymnospermae. 
Class  I.     Pinoideae. 

Order.     Coniferales  (cone-bearing  plants). 
Family.    Pinaceae  (pine  family). 
Genus.    Pinus  (the  pines) . 
Species,    laricio  (Austrian  pine). 

B.  Habitat: 

The  Coniferales  are  widely  distributed  over  the  earth's 
surface,  often  forming  extensive  forests.  The  genus 
Pinus  occurs  in  North  America  throughout  Canada 
and  the  northern  United  States,  from  the  Atlantic  to 
the  Pacific  coasts.  The  white  pine  (Pinus  Strobus) 
occurs  from  Canada  south  along  the  Alleghanies  to 
Georgia,  and  west  to  Illinois  and  Iowa.  The  western 
yellow  pine  (P.  ponderosa)  extends  south  to  western 
Nebraska,  Texas,  Mexico,  and  California.  The  long- 
leaved  or  "Georgia  pine"  (P.  palustris)  is  found  near 
the  coast  from  Virginia  to  Florida,  and  Texas.  The 
spruce-pine  (P.  echinata)  also  occurs  as  far  south  as 
Florida,  and  in  Illinois,  Kansas,  and  Texas.  Consider- 
able forests  of  it  are  found  in  southern  Missouri.  The 
loblolly  pine  (P.  tceda)  extends  along  the  coast  from 
Delaware  to  Texas  and  north  up  the  Mississippi 
Valley  to  Arkansas.  Pinus  laricio  is  not  native  to  the 
United  States,  but  has  been  introduced  into  cultiva- 
tion, as  has  also  P.  sylvestris,  the  "Scotch  pine,"  of 
northern  Europe,  and  other  species. 
Pine  wood  was  formerly  one  of  the  most  valuable  and 

II  161 


1 62  MORPHOLOGY  AND  LIFE  HISTORY 

at  the  same  time  one  of  the  cheapest  of  soft-wood 
timbers,  but  owing  to  an  utter  disregard  of  the  prin- 
ciples of  scientific  forestry,  it  is  now  one  of  the  scarcest 
and  most  expensive.  Regions  that  were  formerly 
extensively  forested,  and  the  center  of  a  prosperous 
lumber  industry,  are  now  waste  land,  often  occupied  by 
tall  stumps,  and  a  source  of  no  profit.  It  is  not  neces- 
sary to  destroy  the  forests  in  order  to  obtain  an  abun- 
dant supply  of  lumber,  provided  only  that  the  crop  be 
harvested  in  accordance  with  scientific  principles. 
The  conservation  of  the  forests  is  one  of  the  most  important 
economic  problems  confronting  our  country,  and  excellent 
opportunities  are  now  offered  for  well-trained  foresters. 

VEGETATIVE  ORGANS 
C.  The  Stem: 

1.  In  Pinus  the  shoot,  as  usual,  is  composed  of  the 
stem  and  the  leaves.     The  stem  is  divided  into  a 
main  part,  or  trunk,  and  lateral  branches.     The 
entire  portion  of  the  shoot,  except  the  trunk,  is 
designated  by  foresters  as  the  crown1  of  the  tree. 

2.  The  following  observations  (C,  3-10)  of  the  stem 
as  a  whole  are  to  be  made  out  of  doors,  recorded 
at  this  place  in  the  laboratory  notes,  and  handed  in 
at  the  next  class  period. 

3.  Designate  the  type  of  the  trunk  as  excurrent  (i.e., 
extending,  entire  from  the  ground  to  the  apex  of  the 
tree),  or  deliquescent  (i.e.,  extending  entire  for  only 
a  short  distance  from  the  ground,  and  then  sub- 
dividing  into    the   numerous   limbs   and   smaller 
branches  of  the  crown1). 

xThe  use  of  the  term  crown  in  this  sense  is  quite  different  from  its 
older  use  by  plant  anatomists  to  designate  the  region  (usually  at  or  near 
the  surface  of  the  ground)  where  the  root  and  shoot  join. 


PINUS   LARICIO  163 

4.  Describe  variations  in  the  diameter  of  the  trunk. 

5.  Do  you  find  prominent  swellings  (buttressing  roots) 
at  the  base  of  the  trunk?    If  so,  suggest  their 
possible  advantage  to  the  tree.1 

6.  Describe  the  outline  of  the  crown  as  flat,  conical,  or 
cylindrical. 

7.  Describe  the  appearance  of  the  bark. 

8.  Note  that  the  lateral  branches  appear  to  be  given 
off  in  whorls,  or  circles,  at  regular  intervals  along 
the    trunk.     Observe   closely   and   state   whether 
these  are  true  whorls  (i.e.,  the  component  branches 
in  exactly  the  same  horizontal  plane),  or  pseudo- 
whorls  (i.e.,  the  branches  not  really  in  the  same 
plane). 

9.  Do  you  find  enlargements  on  the  under  side  of  the 
larger  limbs  at  the  base?    Suggest  any  advantage 
this  may  be  to  the  limb;  the  conditions  resulting 
in  their  formation. 

10.  Draw  a  diagram  illustrating  all  points  observed 

under  C,  1-9.     Make  the  trunk  15  dm.  high. 
D.  The  Vegetative  Branches: 

1.  In  specimens  furnished,  note  the  two  kinds  of  vege- 
tative branch:    The  main  or  "long"  branch,  bear- 
ing scale-like  leaves,  and,  in  the  axils  (upper  angle 
made  by  the  leaf  with  the  branch  that  bears  it)  of 
these  scales,  the  dwarf  branches,  bearing  the  foliage- 
leaves  or  pine  "needles."    In  what  does  the  long 
branch  terminate? 

2.  The  Long  Branch. 

(a)  Describe   the   arrangement    (spiral)    and   dis- 
tribution of  the  dwarf  branches  on  the  long  ones. 

(b)  Note  the  rings  of  dry  bud-scales  or  scale-scars 


conditions  favoring  the  formation  of  buttresses  should  be  dis- 
cussed in  class. 


1 64  MORPHOLOGY  AND  LIFE  HISTORY 

at  intervals  along  the  branch.  The  sections 
of  the  branch  between  these  rings  represent  the 
amount  of  each  year's  growth  in  length.  Ascer- 
tain the  age  of  your  specimen. 

(c)  State  several  ways  in  which  younger  portions 
of  the  stem  may  be  distinguished  from  older. 

(d)  For  how  many  years  do  the  dwarf  branches 
remain   attached?    The   scales   that   subtend 
them?    Observe  the  scars  left  by  the  fallen 
dwarf  branches. 

(e)  Illustrate  by  a  drawing  the  features  observed 
under  D,  2,  (a)-(d). 

(f)  Measure  and  record  the  amount  of  each  annual 
growth  in  length. 

(g)  Draw  a  horizontal  line  as  many  decimeters  long 
as  your  specimen  is  years  old.    Mark  off  the 
line  into  decimeter  spaces,  and  at  the  end  of  each 
decimeter  erect  a  perpendicular  as  many  milli- 
meters high  as  the  branch  grew  during  the  corre- 
sponding  year.     Connect   the   tops   of   these 
perpendiculars  by  a  gently  curving  line,  which 
will  be  the  curve  of  annual  growth  in  length 
for  the  period  covered. 

(ti)  Suggest  reasons  for  the  observed  differences  in 
amount  of  annual  growth;  for  the  direction  of 
growth  taken  by  the  branch  at  various  times. 

(i)  Make  a  diagram  of  a  cross-sectional  view  of  the 
branch,  and  describe  the  relative  position  of 
wood,  pith,  and  bark.  Does  the  bark  contain 
any  chlorophyll?  If  so,  in  what  region  is  it 
found? 
3.  The  Dwarf  Branch. 

(a)  Do  you  find  nodes  and  internodes,  or  any 
other  evidence  that  these  branches  grow  in 


PINTJS   LARICIO  165 

length  each  year?    Find  evidence  that  they 
do  not. 

(b)  Compare  the  number  of  needles  borne  by  each 
dwarf  branch.    Is  the  number  constant?    On 
what  part  of  the  branch  are  they  borne? 

(c)  Note  the  bud-scales,  some  of  which  form  a 
sheath  about  the  bases  of  the  needles. 

The  Foliage-leaves. 

(a)  Describe  their  shape.    Are  they  differentiated 
into  petiole  and  blade? 

(b)  Make  a  drawing,  natural  size,  of  an  entire  leaf, 
and  a  diagram  (X  10)  of  a  cross-sectional  view. 

The  Terminal  Bud. 

(a)  Describe    its    color,    coverings    (bud-scales), 
and  shape.     Draw  (X  3). 

(b)  With  the  scalpel  remove  one  of  the  bud-scales 
at  its  base.     Describe  and  draw  (X  5). 

(c)  Now  remove,  one  at  a  time,  the  remaining  bud- 
scales,  having  care  not  to  break  or  injure  the 
tender  inner  tissues. 

(d)  Describe  the  place  and  mode  of  attachment 
of  the  scales. 

(e)  Explain  how  they  are  adapted,  in  structure  and 
position,  to  protect  the  bud.     From  what  do 
they  protect  it? 

(/)  Describe  the  color  of  the  inner  tissues.  Can 
Pinus  form  chlorophyll  in  the  dark?  Explain. 

(g)  Make  a  drawing  (X  5)  of  the  bud  after  the 
scales  have  been  removed. 

(ti)  With  a  sharp  scalpel  make  a  median  longi- 
tudinal section  of  the  bud.  Observe  the  central, 
conical  axis,  bearing  thin  membranous  scales. 
In  the  axile  of  each  scale  find  a  small  knob-like 
outgrowth. 


1 66  MORPHOLOGY  AND   LIFE  HISTORY 

(*)   Make  a  drawing  (X  10)  of  the  longitudinal  view. 
(k)  Into  what  will  the  bud  develop?    What  will 

become  of  each  of  its  parts? 
(/)    How  much  of  your  specimen  represents  last 

year's  terminal  bud?    The  bud  of  year  before 

last? 
(m)  When  the  annual  growth  of  a  branch  ends  with 

the  formation  of  a  bud  the  growth  is  called 

determinate.    Is    the   growth   of    the    dwarf 

branches   determinate   or  indeterminate?    Of 

the  long  branches? 
E.  Eomologies: 

1.  Organs  which  perform  like  functions  are  analogous 
to  each  other.    Organs  which  correspond  to  each 
other  structurally,  i.e.,  which  have  the  same  mor- 
phological value,  are  homologous.    For  example, 
the  flat,  chlorophyllous  stems  of  cacti  and  the  foliage 
leaves  of  the  maple  tree  are  analogous,  for  they  both 
function  as  organs  of  photosynthesis;  but  they  are 
not  homologous,  for  one  is  a  stem,  the  other  a  leaf. 
The  bud-scales  of  Pinus  and  the  pine  "needles" 
are  homologous,  i.e.,  from  the  standpoint  of  struc- 
tural value  (morphological  standpoint)   they  are 
both  leaves.    But   they  are  not  analogous,   for, 
whereas  the  "needles"  act  as  organs  of  photo- 
synthesis, the  bud-scales  do  not,  as  they  have  no 
chlorophyll. 

2.  One  of  the  most  important,  and  often  most  difficult, 
problems  of  morphology  is  correctly  to  interpret 
the  structural  value  of  an  organ;  in  other  words,  to 
recognize  homologies;  for  any  organ  may  be  pro- 
foundly modified,  and  appear  so  disguised  as  to 
make  it  extremely  difficult  to  recognize  its  morpho- 
logical significance.    Pinus  furnishes  an  excellent 


PINTJS   LARICIO  167 

illustration  of  the  modification  of  organs  for  various 
functions. 

3.  Enumerate  all  the  homologs  of  the  foliage-leaf 
found  thus  far  on  Pinus,  and  show  why  the  organs 
you  name  are  homologous. 

REPRODUCTION 

F.   The  Staminate  Cone: 

1.  On  which  portion  of  the  vegetative  branch  are  the 
staminate  cones  borne?    Do  they  extend  clear  to 
the  tip  of  the  branch,  i.e.,  are  they  ever  terminal? 
In  what  does  the  tip  of  the  branch  that  bears 
them    terminate?    Ascertain    their    length    and 
greatest  diameter  in  millimeters. 

2.  Are  the  cones  subtended  by  (i.e.,  borne  in  the  axil 
of)  a  scale-like  leaf?    Note  whether  they  are  sessile 
or  stalked? 

3.  Observe  the  spiral-like  arrangement  of  the  micro- 
sporophylls  of  the  cone. 

4.  The  staminate  cones  are  modified  branches.    To 
which  of  the  vegetative  branches  are  they  homolo- 
gous? 

5.  Make  a  diagram  (X  2)  showing  the  mode  of  attach- 
ment of  the  cone  and  the  subtending  scale. 

6.  With  a  razor  bisect  a  cone  longitudinally  and  ob- 
serve the  central  axis,  bearing  the  microsporophylls, 
or  stamens. 

7.  With  the  aid  of  a  hand  lens,  or  dissecting  micro- 
scope, observe  the  short  stalk  of  each  stamen  and, 
on  the  under  (dorsal)  side  of  the  broadened  stalk, 
two   small  pouches,   the  pollen-sacs   (microspor- 
angia),  containing  pollen-grains. 

8.  Make  a  diagram  (X  10)  of  the  cone  as  seen  in  longi- 
tudinal section. 


l68  MORPHOLOGY  AND  LIFE  HISTORY 

9.  Remove  an  entire  stamen  and  observe  that  the 
tip  of  it  is  turned  up  so  as  to  fit  over  the  end  of  the 
stamen  next  above  it.  Suggest  any  advantage  in 
this  arrangement. 

10.  Make  a  drawing  to  illustrate  this  feature. 

11.  Make  a  cross-section  of  the  stamen  and  ascertain 
of  how  many  pollen-sacs  it  is  composed.     Draw. 
The  pollen-sacs  of  the  stamen  constitute  the  anther. 

12.  The  structure  of  the  staminate  cone  shows  it  to  be 
in  reality  a  simple  flower.     It  is  homologous  to  the 
staminate  flower  of  some  of  the  higher  plants.    To 
what  in  Zamia  is  it  homologous? 

G.   The  Young  Male  Gametophyte: 

1.  Mount  several  mature  pollen-grains  in  water  and 
examine  with  the  high  power. 

2.  Observe  the  body  of  the  grain,  and  the  two  lateral 
wing-like  expansions,  developed  from  the  outer  coat 

of  the  pollen-grain.     Suggest  their  use. 

3.  Within  the  grain  observe  the  tube-nucleus  near  the 
center,  and  the  generative  cell  near  the  wall  farthest 
from   the  wings.    Look  for   the  prothallial  cell, 
which  frequently  may  be  seen  between  the  wall  of 
the  grain  and  the  generative  cell. 

4.  Make  a  drawing,  25  mm.  broad,  showing  all  features 
observed  under  G,  1-3. 

5.  The  nuclear  and  cell-divisions  which  give  rise  to 
these  structures  are  steps  in  the  germination  of  the 
microspore.     Into  what  does  the  microspore  of  the 
heterosporus  pteridophytes  develop  by  germina- 
tion?   To  what,  then,  in  Isoetes  or  Selaginella,  is 
the  mature  pollen-grain  of  Pinus  homologous? 

6.  If  prepared  microscopic  slides  are  available,  more 
detailed  study  may  be  made  of  the  structure  of  the 
pollen-grain. 


PINUS   LARICIO  169 

H.  The  Young  Carpellate  Cone: 

1.  On  which  internode  of  the  vegetative  branch  are 
the  carpellate  cones  borne?    On  what  part  of  the 
branch?     Do  they  occur  singly  or  in  clusters?     As 
terminal  or  as  lateral  outgrowths? 

2.  Note  that  each  carpellate  cone  is  borne  at  the  tip 
of  a  stalk.     Describe  any  outgrowths  on  this  stalk. 

3.  Describe  the  attitude  of  the  cone  at  the  time  of 
pollination,  as  erect  or  pendant. 

4.  Observe  the  spiral  arrangement  of  the  cone-scales, 
somewhat  more  marked  than  in  the  staminate  cone. 
In   fresh   specimens    the    cone-scales   are   slightly 
separated  from  each  other  at  the  time  of  pollina- 
tion.    Explain  the  advantage  of  this. 

5.  Make  a  drawing  (X  2)  of  the  cone  with  the  stalk 
that  bears  it. 

6.  Make  a  median  longitudinal  section  of  the  cone  and 
stalk,  and  represent  by  a  drawing  all  parts  seen. 

7.  Carefully  dissect  off  one  of  the  central  cone-scales, 
being  sure  to  note  which  is  the  inner  (ventral)  and 
which  the  outer  (dorsal)  surface  of  the  scale,  and 
observing  the  membranous  bract  which  subtends  it. 

8.  On  the  inner  surface  of  the  scale,  near  the  base, 
observe  with  the  hand  lens  two  ovules,  each  with 
two  little  prongs,  between  which  is  the  pollen- 
chamber;  between  and  above  the  ovules  a  pointed 
outgrowth. 

9.  Make  drawings  (X  10)  of  the  ovuliferous  scale  as 
seen  (a)  from  the  side;  (b)  from  the  outer  surface, 
showing   the  bract;   (c)   from   the  inner   surface, 
showing  the  ovules. 

10.  The  ovules  are  megasporangia  surrounded  by  a 
protecting  integument. 

11.  There  is  some  evidence  for  considering  the  ovuli- 


170  MORPHOLOGY  AND   LIFE   HISTORY 

f erous  scale  and  the  bract  that  subtends  it  as  a 
megasporophyll,  or  carpel.  On  the  basis  of  this 
interpretation  the  bract  would  be  homologous  to  the 
ligule  in  Isoetes  or  Selaginella.  But  other  facts 
argue  against  this  theory,  and  lead  to  different 
interpretations,  so  that  the  exact  homology  of  the 
organ  is  in  doubt.  Possibly  it  represents  two  mega- 
sporophylls  or  carpels.  If  so,  we  must  interpret  the 
carpellate  cone,  not  as  a  flower,  like  the  staminate 
cone,  but  as  inflorescence,  or  cluster  of  flowers,  each 
scale  representing  a  flower. 
/.  The  Mature  Male  Gametophyte: 

During  the  first  spring  pollination  takes  place,  as 
described  in  the  text-book,  and  the  growth  of  the 
pollen-tube  begins.  Its  growth  is  very  slow,  however, 
until  the  following  spring,  when  the  growth  becomes 
more  vigorous.  The  tube-nucleus  passes  to  the  tip  of 
the  pollen-tube,  which  penetrates  the  tissues  of  the 
nucellus  (/,  6,  p.  156),  digesting  a  channel  for  itself  as  it 
grows,  usually  branching,  and  feeding  on  the  digested 
tissue.  The  generative  cell  divides  into  a  body-cell 
and  a  stalk-cell,  and  the  nucleus  of  the  body-cell 
again  divides  into  two  sperm-nuclei. 
K.  The  Female  Gametophyte: 

Near  the  time  of  pollination  the  megaspore  consists  of 
one  uninucleate  cell  (the  one-celled  stage  of  the  embryo- 
sac).  By  repeated  nuclear-divisions  the  nucleus  of  the 
megaspore  gives  rise  to  a  large  number  of  nuclei,  which 
at  first  lie  free  in  the  surrounding  cytoplasm;  but  later 
each  of  these  nuclei  organizes  about  itself  a  cell, 
surrounded  by  cell- walls.  The  tissue  thus  formed 
within  the  embryo-sac,  and  enlarged  by  growth,  forms 
the  young  female  gametophyte  (endosperm).  The 
megasporangium,  surrounding  the  endosperm,  is  called 


PINUS   LARICIO  171 

the  nucellus,  as  in  Zamia,  and  both  these  structures  are 
surrounded  by  a  protecting  envelope,  the  integument. 
The  pollen-chamber  lies  between  the  tip  of  the  nucellus 
and  the  integument.  The  micropyle  leads  through 
the  integument  to  the  pollen-chamber.  In  the  pol- 
lination of  Pinus  the  entire  pollen-grain  passes  into 
the  pollen-chamber  through  the  micropyle. 

L.   The  Ovule: 

The  endosperm,  nucellus,  and  integument  together 
form  the  young  ovule.  Nearly  one  year  is  required 
for  its  development  to  the  stage  described  above.  In 
the  second  spring,  while  the  pollen-tube  is  rapidly 
elongating,  and  the  nuclear  divisions,  noted  above  are 
taking  place  within  it,  several  archegonia  develop  in 
the  micropylar  end  of  the  endosperm.  In  the  venter 
of  each  archegonium  lies  the  large  egg. 

M .  Fertilization: 

Eventually  the  pollen- tube  enters  the  neck  of  an  arche- 
gonium (compare  with  the  process  in  Zamia  and  other 
Cycads),  its  contents  are  discharged  into  the  venter, 
and  one  of  the  sperm-nuclei  fuses  with  the  nucleus  of 
the  egg.  Thus  fertilization  is  accomplished,  about  one 
year  after  pollination.  The  transfer  of  the  sperm- 
nucleus  to  the  egg  by  means  of  a  pollen-tube  is  called 
siphonogamy,  and  plants  in  which  this  occurs, 
Siphonogamia. 

The  one-year-old  cone,  to  be  studied  next,  represents 
the  stage  of  development  at  about  the  time  of  fertiliza- 
tion. The  sperms  of  Pinus  are  non-motile. 

N.  The  One-year-old  Carpellate  Cone: 

1.  Compare  the  position  on  the  branch,  and  the  atti- 
tude of  the  one-year-old  cones  with  that  of  the  cones 
at  the  time  of  pollination. 

2.  Study  these  cones  as  directed  above  (H,  i-n),  com- 


172  MORPHOLOGY  AND   LIFE  HISTORY 

paring  the  older   and   the  younger  organs.     En- 
deavor to  explain  any  differences  observed. 
3.  Record  the  length  and  greatest  diameter  of  the  one- 
year-old  cone,  and  make  a  drawing  of  it,  natural 
size. 
O.  The  Two-year-old  Carpellate  Cone: 

1.  Record,  its  position  on  the  branch,  its  attitude,  and 
dimensions.     Compare  it,  in  these  points,  with  the 
young,    and   one-year-old   cones.    Draw,    natural 
size. 

2.  Make  drawings  of  a  detached  scale  as  seen  from 
(a)  the  outer  (dorsal)  surface,  (b)  the  inner  (ventral) 
surface,     (c)     the    side.     Describe    any    changes 
observed  in  the  appearance  and  relation  of   the 
various  points. 

3.  Note  that  the  ovule  has  developed  into  a  winged 
seed. 

P.  The  Seed:1 

1 .  The  seeds  are  usually  shed  from  the  pine  cone  during 
the  third  summer,  about  two  years  and  a  quarter 
after  pollination. 

2.  Record  the  dimensions,  shape,  and  character  of  the 
surface  of  the  seed.    The  small  depression  in  the 
smaller  end  of  the  seed  locates  the  micropyle,  which 
is  now  grown  together.    Draw,  natural  size. 

3.  Let  fall  from  a  height  of  several  feet  a  seed  of  some 
species  having  wings  still  attached,  and  note  the 
approximate  time  required  to  reach  the  ground. 
Remove  the  wing  and  repeat  the  observation.     Sug- 
gest a  use  of  the  wing.    Is  it  very  firmly  attached 
to  the  seed? 

4.  Remove  the  tough,  outer  seed-coat  (testa),  which  is 

1  The  large  seeds  of  the  nut-pine,  Pinus  edulis,  or  of  Pinus  pinea,  may 
advantageously  be  used  for  this  study. 


PINUS   LARICIO  173 

the  mature  integument,  referred  to  in  K  and  L 
(p.  170-171).  The  integument  is  analogous  to  an 
indusium.  Why? 

5.  Underneath  the  testa,  observe  the  thin,  membran- 
ous inner  seed-coat,  formed  by  a  separation  and 
differentiation  of  an  inner  layer  of  the  tissue  of  the  in- 
tegument.    Describe  its  color  and  surface-character 
as  seen  under  the  hand  lens.     Compare  with  Zamia. 

6.  Observe  the  small  hole  through  the  micropylar  end 
of  the  inner  coat.     What  does  this  represent? 

7.  Remove  the  inner  seed-coat,  having  care  not  to  dis- 
turb the  brownish,  membranous  cap  on  the  micro- 
pylar end  of  the  kernel.     This  cap  is  the  remains 
of  the  nucellus  (megasporangium) .     Note  the  modi- 
fication of  its  tissue  at  the  place  through  which  the 
pollen- tube  passed  on  its  way  to  the  embryo-sac. 
The  remainder  of  the  nucellus  was  consumed  by 
the  female  gametophyte  during  the  development  of 
the  latter. 

8.  What  is  the  homology  of  the  white,  fleshy  kernel 
of  the  pine  seed. 

9.  Make  a  drawing  (X  4)  of  the  endosperm  and  nu- 
cellus. 

10.  Remove  the  nucellar  tissue.     Is  it  firmly  attached 
to  the  endosperm?    Describe  the  appearance  of  the 
endosperm  under  the  nucellar  cap. 

11.  Very  cautiously  separate  the  endosperm  into  longi- 
tudinal halves.    Begin  the  dissection  at  the  end 
opposite  the  micropylar  end  so  as  not  to  injure  the 
embryo-sporophyte  within. 

12.  Observe  that  the  embryo  lies  in  a  distinct  cavity  or 
chamber,  its  tissues  being  quite  distinct,  anatomic- 
ally, from  those  of  the  gametophyte.      Can  you  ac- 
count for  the  formation  of  this  cavity  ? 


174  MORPHOLOGY  AND  LIFE  HISTORY 

13.  Note  that  the  embryo  is  composed  of  a  main  axis, 
bearing  a  whorl  of  cotyledons  borne  near  one  end. 
Can  you  detect  distinct  regions  of  the  axis?    If  so, 
how  many,  and  how  are  they  distinguished?    How 
many  cotyledons  are  there?    Is  the  number  always 
either  odd  or  even? 

14.  Observe  that  the  embryo  is  attached  at  the  end 
opposite  the  cotyledons  to  a  slender  filament,  the 
suspensor.    At  this  end  of  the  embryo-chamber 
may  frequently  be  seen  the  disorganized  remains  of 
other  embryos   that  failed  to  develop.     In  rare 
instances  two  embryos  develop  in  one  seed.    This 
is  called  polyembryony,  a  condition  very  common 
in  lemons,  and  other  citrous  fruits. 

15.  Make  a  drawing  of  the  young  sporophyte,  50  mm. 
long. 

16.  Make  a  median  longitudinal  section  of  the  embryo, 
and  observe  that  the  portion  of  the  axis  below  the 
cotyledons    (hypocotyl)    is   encased   in  an   outer, 
strongly  developed  root-cap,  which  completely  en- 
closes the  hypocotyl.     Note  further  that  the  coty- 
ledons are  borne  on  the  hypocotyl.     From  its  op- 
posite end  (radicle-end)  the  tap-root  will  develop. 
The  hypocotyl  is  the  first  internode  of  the  sporo- 
phyte.   Where  is  the  first  node? 

17.  At  the  summit  of  the  axis,  above  the  cotyledons  and 
surrounded  by  them,  observe  the  conical  epicotyl. 
It  will  develop  into  the  second  and  subsequent 
internodes.     Explain    the    meaning    of    the    term 
epicotyl. 

18.  Construct  three  diagrams  (X  5)  showing  (a)  the 
entire  seed  in  longitudinal  section  (the  embryo  not 
sectioned);  (6)  a  cross-section  of  the  seed,  passing 


PINUS   LARICIO  175 

through  the  cotyledons  and  epicotyl;  (c)  a  cross- 
section  of  the  seed  passing  through  the  hypocotyl. 
Q.  The  "Germination"  of  the  Seed: 

1.  Observe  specimens  of  seeds  and  seedlings  represent- 
ing various  stages  of  germination. 

2.  Describe  (a)  the  changes  that  the  various  parts  of 
the  seed  undergo,  in  shape,  size,  and  position;  (b) 
the  manner  in  which  the  seedling  breaks  through 
the  surface  of  the  soil,  and  the  advantage  of  this; 
(c)  the  relative  rate  of  early  growth  of  the  root  and 
shoot,  and  the  significance  of  this;  (d)  color-change 
in  the  cotyledons,  its  significance  and  whether  or 
not  it  can  take  place  in  darkness;  (e)  the  fate  of  the 
endosperm,  and  the  evident  r61e  of  this  tissue;  (/) 
the  manner  of  shedding  the  seed-coat;  (g)  the  place 
of  development  and  character  of  any  new  organs. 

3.  Compare  the  germination  of  a  seed,  with  that  of  a 
spore.    What,  in  reality,  is  the  germination  of  a 
seed? 

R.  General  Questions: 

1.  To  which  alternating  generation  does  the  pine  tree 
belong? 

2.  In  a  well- worded  paragraph  compare  the  relation 
of  gametophyte  and  sporophyte  in  the  moss,  fern, 
Isoetes  (or  Selaginella)t  and  Pinus. 

3.  State  the  relative  prominence  of  the  sexual  and 
asexual  generations  in  plant-groups  of  successively 
higher  organization. 

4.  When  the  young  sporophyte  of  Pinus  begins  growth 
does  it  grow  continuously  to  maturity,  or  does  a 
period  of  rest  intervene?     Compare  it  with  Isoetes 
or  Selaginella  in  this  respect. 

•5.  What  changes  would  result  in  the  formation  of  a 
seed  in  Isoetes?    What  interferes  with  seed-forma- 


176  MORPHOLOGY  AND  LIFE  HISTORY 

tion  in  that  group?    What  changes  would  interfere 
with  seed-formation  in  Pinus? 

6.  Define  a  seed.     State  several  advantages  to  the 
plant  of  the  seed-habit. 

7.  To  what,  in  the  fern,  is  the  endosperm  of  the  pine 
seed   homologous?     To   what  in   the   moss?     To 
what,  in  Isoetes  or  Selaginella,  is  the  pollen-grain 
homologous?     To  what  in  the  fern?     State,  with 
reasons,  whether  the  leaves  of  the  moss-plant  are 
homologous  or  analogous  (or  neither)  to  pine  need- 
les.    In  like  manner,  compare  the  organs  of  fixation 
of  the  moss-plant,  of  the  fern-plant,  of  the  fern- 
prothallus,  and  of  the  pine  tree. 

8.  Diagram  the  life  cycle  of  Pinus  as  directed  for 
Isoetes    (E,   3,   p.  139),  substituting  pg(  =  pollen- 
grain)  for  #w(  =  microspore),  and  es(  =  embryo-sac) 
for  W£ 


Trillium  (WAKE-ROBIN) 

A.  Classification: 

Division  VII.     Spermatophyta. 
Subdivision  B.    Angiospermae  (seeds  enclosed  in  an 

ovary) . 
Class  I.     Monocotyledoneae    (embryo   with    one 

lateral  cotyledon). 
Order.    Liliales  (lily  order). 
Family.    Liliaceae  (lily  family). 

Genus.     Trillium  (Latin  ires,  three). 
Species,     (e.g.,  sessile)    (sessile  flowered 
trillium).1 

B.  Habitat: 

All  species  of  Trillium  occur  in  the  woods  in  early 
spring,  and  the  genus  has  a  geographic  range  extend- 
ing from  Nova  Scotia  westward  to  Manitoba,  and 
southward  as  far  as  Florida. 

1  Any  species  of  Trillium  may  be  used,  with  minor  changes  in  the  direc- 
tions; or,  in  fact,  any  other  convenient  genus  of  the  Liliaceae. 

NOTE. — There  are  nearly  25,000  different  species  of  Monocotyledons. 
The  order  Liliales,  comprising  about  5,000  species,  contains  the  most 
highly  developed  types.  The  lower  Monocotyledons  have  naked  flowers 
(i.e.,  no  sepals  and  petals),  with  the  parts  spirally  arranged,  as  in  the  Gym- 
nosperms.  The  higher  ones  have  the  parts  of  the  flower  arranged  in  con- 
centric circles  or  cycles,  five  in  number  (pentacyclic),  with  usually  three 
members  in  each  cycle.  Our  knowledge  of  the  monocotyledons  is  not  yet 
adequate  to  make  possible  a  satisfactory  classification.  Taxonomists 
differ  in  various  points.  The  authors  of  Gray's  "New  Manual"  (yth 
Edition,  1908)  subdivide  the  Liliacese  into  Tribes.  Trillium  is  in  the  tribe, 
Paridea.  Britton  ("Manual  of  the  Flora  of  the  Northern  States  and 
Canada")  and  others,  divide  the  Liliaceae,  as  given  in  Gray,  into  four  or 
more  families,  the  trilliums  being  in  the  Convallariacea,  or  Lily-of-the- 
valley  family. 

12  177 


178  MORPHOLOGY   AND   LIFE   HISTORY 

C.  The  Shoot: 

1.  General. 

(a)  Note  its  division  into  a  main,  thickened  under- 
ground part  (rhizome) ,  bearing  numerous  roots, 
and  a  long  slender  aerial  branch. 

2.  The  Rhizome. 

(a)  Describe  its  attitude  (horizontal  or  erect),  and 
its    general    appearance.     Compare    Trillium 
with  the  fern  in  this  respect. 

(b)  Are  there  branches,  besides  the  aerial  branch? 

(c)  Note   the   thin    membranous   scales   near   the 
apical  end.     Record  their  number  and  position. 
Carefully  remove  them  with  the  scalpel.     What 
purpose    may    they    serve?     What    is    their 
homology?     Make  a  drawing  of  one  (X  i). 

(d)  Observe    the   nodes    and   internodes.    What 
do  the  nodes  represent?     Note  the  remnants  of 
the  old  scales  at  each  node.     Compare   the 
lengths  of  the  internodes.     What  is  the  mean- 
ing of  this? 

(e)  Describe  any  other  scars  on  the  rhizome.     Are 
they  on  nodes  or  internodes?     What  do  they 
represent? 

(/)  State,  with  reasons  for  your  opinion,  the  age 
of  your  specimen. 

3.  The  Aerial  Branch. 

(a)  Describe  its  general  appearance,  shape,  length 
(compare  several  different  specimens),   color- 
ation (color-pattern),  and  presence  or  absence 
of  branches. 

(b)  At  which  end  of  the  rhizome  is  it  borne?     Is 
it  a  terminal  or  a  lateral  outgrowth?     Is  it  an 
axillary  organ  (i.e.,  borne  in  the  axil  of  a  leaf), 
or  not?    On  a  node  or  an  internode? 


TRILLIUM  179 

(c)  Make  a  drawing  20  mm.  in  diameter,  showing 
the  distribution  of  the  fibro-vascular  bundles 
as  seen  in  cross-section. 

(d)  What  does  the  branch  bear  at  its    summit? 
Do  you  find  any  exceptions  to  this? 

D.  The  Roots: 

1.  Describe  their  distribution  on  the  root-stalk.     Do 
they  occur  on  both  nodes  and  internodes?     State 
the  significance  of  the  observed  distribution. 

2.  Record  the  presence  or  absence  of  branching. 

3.  Compare  the  appearance  of  new  roots  with  that 
of  older  ones.     On  what  part  of  the  rhizome  are 
they  borne? 

4.  Describe  the  surface  appearance  of  older  roots. 
Remove  a  root  3  to  4  cm.  long,  hold  it  by  each  end 
and  gently  pull  (not  hard  enough  to   break  the 
root).     How  does  this  affect  the   surface  appear- 
ance?    How   do   you  think    the   original  feature 
was  produced? 

5.  With  the  scalpel  cut  a  root  squarely  off  near  its 
base  and  observe  the  cross-sectional  view.     Dis- 
tinguish three  tissue-systems:  (a)  the  epidermis; 
(6)  the  central  cylinder;  (c)  between  (a)  and  (ft), 
the  cortex. 

6.  Peel  down  a  strip  of  the  epidermis,  and  observe 
whether  the  wrinkling  is  confined  to  it  or  not. 

7.  Make  a  drawing,  twice  natural  size,  showing  the 
external  features  of  the  rhizome,  together  with  a 
portion  of  the  aerial  branch,  and  roots. 

E.  The  Young  Terminal  Bud:1 

i.  Carefully  remove  the  aerial  branch  and  surrounding 
scales  and  observe  the  terminal  (apical)  bud. 

1  On  account  of  the  large  amount  of  material  required,  it  is  desirable 
to  make  E  and  F  class  demonstrations  by  the  instructor. 


l8o  MORPHOLOGY  AND  LIFE  HISTORY 

2.  Describe  its  color,  shape,  attitude,  and  the  relation 
between  it  and  the  base  of  the  aerial  branch.     Draw 

(X2). 

F.  The  Mature  Terminal  Bud:1 

1.  Use  material  gathered  in  late  autumn,  and  care- 
fully dissect  away  the  outer  bud-scales.     Identify 
the  parts  found  within. 

2.  Make  careful  drawings,  and  interpret  the  signifi- 
cance of  this  observation. 

G.  The  Foliage-leaves: 

1.  Describe  the  number,  location,  and  arrangement 
of  the  foliage-leaves.    Are  they  petiolate  or  sessile? 

2.  Observe: 

(a)  The  coloration   (described,   for   T.  sessile,   as 

"blotched"). 

(V)  The  outline  of  the  base,  apex,  and  margin. 
(c)  The  venation. 
H.  The  Flower: 

1.  On  what  part  of  the  shoot  is  it  borne?    Record 
the  presence  or  absence  of  a  flower-stalk  (peduncle). 
Explain  the  significance  of  the  specific  name  of 
this  species  (T.  sessile).    Has  the  flower  an  odor? 
If  so,  describe  it. 

2.  Observe. 

(a)  The  outer  circle  of  parts   (calyx)   composed 
of   separate   sepals.    How   many   sepals  are 
there?    Describe  them  as  you  did  the  leaves. 
NOTE. — The  term  calyx  comes  from  the  Greek 
word  kalyx,  a  cover;  the  verb  is  kalypto,  to 
cover.    What  organ  of  the  moss  has  its  name 
derived  from  the  same  source  as  calyx? 

(b)  The  circle  of  parts  (corolla)  next  within  the 
the  calyx,  composed  of  separate  petals.    How 


TRILLIUM  l8l 

many  petals?  Are  they  opposite  or  alternate 
with  the  sepals?  Record  their  color  in  fresh 
(not  preserved)  specimens.  Describe  a  petal 
as  you  did  the  leaf  and  sepal. 

(c)  With  the  corolla,  a  circle  of  three  microsporo- 
phylls  (stamens)  each  opposite  a  sepal.    By 
carefully    bending   back  (but  not  removing) 
the  sepals  and  petals,  observe  whether  or  not 
the  other  stamens  are  in  the  same  circle  as 
the  first  ones,  or  in  an  inner  (higher)  circle. 
Describe  their  location  with  reference  to  the 
petals.     Record  the  total  number  of  stamens. 
Note  that  each  stamen  is  composed  of: 

(1)  A  stalk  (filament),  bearing  at  its  tip, 

(2)  An  anther,  composed  of  marginal,  linear 
pollen-sacs  (microsporangia),  and  connect- 
ing   tissue     (the    connective).     Observe 
whether  the  connective  is  prolonged  be- 
yond the  sporangia.    Note  that  the  pollen- 
sacs  dehisce  (open)  on  the  inside  (i.e.y  are 
introrse).    Describe  their  manner   of  de- 
hiscence. 

(3)  What    do  the   pollen-sacs   contain?    De- 
scribe its  color. 

(d)  The  central  pistil  composed  of: 

(1)  The  basal  ovule  case  (ovary) .    How  many 
angles  has  it?    How  many  lobes? 

(2)  The  relatively  long  styles.    How  many? 
Their  inner  surface  is  modified  into 

(3)  A  stigma.    Describe  this  stigmatic  surface 
as  seen  both  with  unaided  eye,  and  under 
the  low  power.    Usually  numerous  pollen- 
grains  may  be  seen  adhering  to  it.    What 
process  has  therefore  taken  place? 


182  MORPHOLOGY   AND   LIFE   HISTORY 

(4)  The  ovary  is  thus  seen  to  be,  not  simple, 
but  compound.  It  is  composed  of  three 
carpels,  bearing  ovules.  Since  the  ovules 
are  megasporangia,  what  is  the  homology 
of  the  carpels? 

3.  Look  up  in  the  dictionary,  and  record  at  this  point, 
the  derivation  of  the  names  of  the  various  parts  of 
a  flower,  studied  above. 

(a)  It  is  important  to  note:  (i)  That  the  various 
cycles  are  each  composed  of  the  same  number 
of  parts;   (2)    that  the  parts  of   the  various 
cycles  alternate  with  each  other. 

(b)  When  the  other  organs  of  a  flower  are  inserted 
below  the  pistil  they  are  said  to  be  hypogynous. 
Is  this  true  of  Trillium? 

(c)  The  more  or  less  enlarged  end  of  the  stem  (or, 
in  non-sessile  forms,  of  the  peduncle)  on  which 
the  organs  of  the  flower  are  inserted,  is  the 
receptacle. 

4.  Make  drawings  as  follows: 

(1)  A  sepal  (X  i);  a  petal  (X  i);  a  stamen  (X  4) 
(both  dorsal  and  ventral  views);  an  imagined 
cross-section  of  an  anther  taken  through  the 
middle  (X4);  the  pistil  (X4);  an  imagined 
cross-section  of  the  pistil  (X  4). 

(2)  A  ground-plan  of  the  flower,  5  cm.  in  diameter, 
first  drawing  five   equidistant  concentric  cir- 
cles, and  filling  in  the  plan  as  directed  by  the 
instructor. 

(3)  An  imaginary  longitudinal  section  of  the  flower 

(X2). 

5.  Compare  the  length  of  the  stamens  with  that  of 
the  pistil.     Carefully  consider  and  state  the  rela- 


TRILLIUM  183 

tive  probabilities  of   self-pollination   and   cross- 
pollination. 

/.  Non-sexual  Reproduction: 

1.  Non-sexual  reproduction  in  Trillium  is  confined  to 
the  growth  of  the  persistent,  underground  rhizome. 
This  organ  is  thick  and  fleshy,  serving  for  the  storage 
of  food. 

2.  Note  the  ridges  and  scars  on  its  surface. 

3.  What  develops  each  year  at  the  growing  end? 

4.  A  plant  that  is  continued  indefinitely,  from  year  to 
year,  by  means  of  a  persistent  root  or  stem,  or  both, 
is  a  perennial;  one  that  persists  for  two  years  only, 
setting  seed  and  dying  at  the  end  of  the  second  sea- 
son is  a  biennial,  plants  that  set  seed  and  perish  at 
the  end  of  one  season  are  annuals.     Name  illus- 
trations of  each  of  these  three  classes  of  plants. 

K.  Sexual  Reproduction: 

1.  Micros  pores. 

(a)  Mount  in  clearing  fluid  (or  water)  on  a  slide 
some  of  the  pollen  from  an  anther. 

(b)  Observe  (first  under  low,  then  under  high  power) 
the    individual    pollen-grains.     Describe    their 
color   and    shape,    and   note    the   network   of 
ridges  on  the  surface  of  each. 

(c)  By  carefully  focusing  on  individual  grains  there 
may  readily  be  detected  in  some  of  them  one 
nucleus,   in  others,    two.     Those  in   the  one- 
nucleate  stage  are  mature  microspores. 

2.  Male  gametophyte.     The  division  of  the  microspore- 
nucleus  is  the  first  stage  in  the  germination  of  the 
spore.     To  what  do  microspores,  when  they  ger- 
minate, give  rise?     What,  therefore,  is  the  homol- 
ogy  of  the  bi-nucleate  pollen-grain? 

(a)  The  larger  nucleus  is  the  tube-nucleus,  and 


1 84  MORPHOLOGY  AND   LIFE   HISTORY 

presides  over  the  development  of  the  pollen- 
tube.  The  smaller  is  the  generative  nucleus. 

(b)  Make  drawings,  2  cm.  in  diameter,  of  a  micro- 
spore  and  of  a  male  gametophyte,  labeling  all 
parts. 

(c)  After  pollination,  the  formation  of  the  pollen- 
tube  takes  place.    This  is  usually  spoken  of  as 
the  "germination  of  the  pollen-grain." 

The  tube  emerges  through  one  of  several  weak 
places  in  the  wall  of  the  grain,  grows  down 
through  the  tissues  of  the  style,  digesting  its 
channel  as  it  proceeds,  or,  in  some  species,  fol- 
lowing a  canal  already  formed  through  the 
style. 

The  generative  cell  (generative  nucleus  with  its 
own  protoplasm)  follows  down  the  pollen-tube, 
and  divides  into  two  non-motile  sperm  cells. 
In  some  species,  e.g.,  Sambucus,  (elder),  this 
division  occurs  before  the  tube  develops.  The 
pollen-tube  passes  through  the  micropyle,  and 
discharges  the  sperm-cells  near  the  egg.  One 
of  the  sperm-nuclei  fuses  with  the  egg-nucleus, 
thus  effecting  fertilization. 

(d)  For    convenience    in    handling    material    the 
observation  of  the  finer  structure  of  the  anther 
and   pollen   will   be    deferred   until  after  the 
microscopic  study  of  the  ovary  and  ovules  (3, 
below). 

3.  Megasporophylls  and  Megasporangia.  With  a  sharp 
scalpel  or  razor  make  a  median  cross-section  of  the 
ovary  and  observe: 

(a)  Its  outline.    Each  of  the  lobes  represents  the 
section  of  one  of  the  carpels  (megasporophylls) , 


TRILLIUM  185 

which  together  compose  the  tri-carpellate, 
compound  ovary. 

(6)  The  number  of  compartments,  ("cells").  Do 
the  septae  (walls)  that  separate  them  meet  in 
the  center?  Compare  the  number  of  cells  with 
the  number  of  carpels. 

(c)  The  placentae  (sing. ,  placenta) ,  or  surfaces  of  the 
septae  to  which  are  attached. 

(d)  The  ovules.    Do  the  ovules  lie  in  a  vertical  or 
in  a  horizontal  plane?    Are  they  few  or  numer- 
ous?   In   Trillium   the   ovules   are   borne   on 
parietal  placentae. 

(e)  The  funiculus  (stalk)  by  which  the  ovule  is 
attached    to    the    placenta.     Observe    (using 
magnifier)  that  the  ovules  have  curved  through 
1 80°,  bringing  their  apical  (micropylar)  ends  to 
their  base  or  point  of  attachment  to  the  fun- 
iculus.    They  are  thus  anatropous  ovules. 

(/")   Make  a  drawing,  4  cm.  in  diameter,  showing 

the  ovary  (and  ovules)  as  seen  in  cross-section. 

4.  Histology  of  the  anther.     Development  of  the  pollen. 

(a)  Use  prepared  slides.    The  sections  on  these 
slides  are  triple-stained  with  safranin,  gentian- 
violet,  and  orange.     By  this  means  the  various 
parts  of  the  cell  are  given  different  colors,  the 
cytoplasm  a  grayish  tinge,  the  nucleolus  and 
chromatin  threads  in  the  nucleus  red,  starch 
grains  a  deep  blue. 

Using  slides  showing  the  microspore-mother-cell 
stage  of  Lilium  canadense,  or  other  convenient 
plant, 

(b)  Observe  the  outline  of  the  section  as  a  whole. 

(c)  The  central  portion  is  the  connective,  contain- 
ing a  vascular  bundle. 


1 86  MORPHOLOGY  AND   LIFE   HISTORY 

(d)  Opposite  the  connective  may  often  be  seen  a 
cross-section  of  the  filament,  with  its  vascular 
bundle. 

(e)  The  numerous,  conspicuous  blue-stained  bodies 
are  starch  grains. 

(/)  Note  the  epidermis,  one  cell  thick.  Does  it 
cover  the  entire  surface?  Does  it  contain 
starch  grains?  Find  numerous  stomata,  each 
with  a  small,  underlying  air-space. 

(g)  At  each  side  of  the  section  will  be  seen  two 
sporangia,  containing  the  large  microspore- 
mother-cells  (pollen-mother-cells) ,  with  promi- 
nent nucleus.  Observe  the  network  of  chrom- 
atin  within  each  of  these  nuclei.  The  mother- 
cells  adhere  more  or  less  closely,  depending 
upon  age.  Their  final  separation  from  other 
cells,  and  from  each  other,  marks  the  first 
separation  of  the  gametophytic  from  the 
sporophytic  generation.  The  mature  micro- 
spore-mother-cell  is  the  first  stage  in  the  develop- 
ment of  the  male  gametophyte  (cf.  6  (a), 
below,  p.  1 88). 

(h)  Around  the  mother-cells  note  a  layer  of  elong- 
ate cells,  radially  arranged,  and  with  nuclei 
more  or  less  disorganized.  These  are  the 
tapetal-cells.  Together  they  form  the  tapetum. 

(i)  Between  the  tapetum  and  epidermis  lie  the 
middle  layers  of  cells  forming  the  wall  of  the 
sporangium.  How  many  cells  thick  is  it? 

(k)  Make  a  drawing  8  cm.  in  longest  measure, 
showing  all  features  observed  under  4,  (a)-(k) . 

(I)  By  two  successive  divisions  each  pollen-mother- 
cell  forms  four  microspores  (young  pollen- 
grains).  They  thus  arise  in  tetrads. 


TRILLIUM  187 

Using  slides  showing  pollen-grains,  observe: 

(m)  The  more  advanced  disorganization  of  the 
tapetal-cells,  including  the  breaking  down  of 
their  cell- walls,  and  the  fragmentation  of  their 
nuclei  into  two  or  more.  These  cells  serve 
to  nourish  the  spore-mother-cells. 

(n)  The  microspores.  Do  they  lie  free  or  con- 
nected? Describe  their  shape,  surface-features, 
and  number  of  nuclei. 

(o)  State  again  the  first  stage  in  the  germination 
of  the  microspore.  What  is  the  resulting 
structure?  What  is  its  homology? 

Megasporangia;  megas pore-mother-cell. 

Using    prepared    slides    showing   the   megaspore- 

mother-cell,  observe: 

(a)  The  outline  of  the  ovary  as  seen  in  cross-section. 

(b)  The   presence   or   absence   of   an  epidermis; 
of  stomata. 

(c)  The  "cells"  of  the  ovary,  each  containing,  in 
the  section, 

(d)  Two  young  ovules  (megasporangia) .    Are  the 
ovules  straight  or  curved? 

At  this  stage  the  tissue  of  the  ovule  is  chiefly 
nucellus,  but  soon  there  develops  at  the  base 
of  the  ovule,  outside  of  the  nucellus, 

(e)  The  inner  integument,  which  grows  up  around 
the  nucellus,  leaving  at  the  summit  only  a 
small  passage, 

(/)  The  micropyle.  Outside  the  inner  integument 
there  usually  develops 

(g)  An  outer  integument.  In  anatropous  ovules 
the  development  of  the  outer  integument 
wholly  or  partially  fails  on  the  side  where  the 
funiculus  adheres  to  the  ovule.  At  the  summit 


1 88  MORPHOLOGY   AND   LIFE   HISTORY 

of  the  nucellus  (apex  of  the  ovule)  is  seen  the 
large 

(ti)  megaspore-mother-cell  (embryo-sac-mother- 
cell),  with  very  prominent  nucleus  and 
nucleolus. 

(i)  Make  a  diagram  of  all  that  you  have  observed 
under  5,  (a)-(ti),  filling  in  the  details  for  one 
ovule. 

6.  Development  of  the  Megaspores. 

(a)  Like  the  microspore-mother-cell,  the  megaspore- 
mother-cell  of  Trillium  divides  twice,  giving 
rise   to  four  megaspores   (tetrads),  but  only 
one  of  these  megaspores  develops  a  gametophyte. 
This  spore  enlarges,  and  by  three  successive 
divisions  gives  rise  to  an  eight-nucleate  female 
gametophyte,  the  embryo-sac.     Three  of  these 
nuclei  organize  antipodal  cells  at  the  basal 
end   of   the   embryo-sac,  and   three   of   them 
organize  cells  at  the  micropylar  end.     One  of 
the  latter  is  the  egg,  the  other  two  thesynergids. 
The  two  remaining  nuclei  fuse  near  the  center 
of  the  embryo-sac,  forming  the  endosperm- 
nucleus  (sometimes    called   definitive  nucleus) , 
but   the   endosperm   does   not   develop   until 
after  the  fertilization  of  the  egg. 

(b)  Unlike   the  microspores,    the  megaspores,   in 
angiosperms,  never  become  free,  independent 
cells,  but  always  retain  an  intimate  physiolog- 
ical connection  with  the   sporophyte   of   the 
next  preceding  generation   (cf.   4 GO,  above). 

7.  The  Embryo-sac. 

(a)  Using  prepared  slides,  study  the  embryo-sac 
in  its  two-  to  eight-celled  stages,  identifying 
the  cells  mentioned  in  6  above.  Draw. 


TRILLIUM  189 

K.  Development  of  the  Embryo: 

i.  After  fertilization  (7,  2,  (c),  p.  184),  the  oosperm 
develops  the  embryo-sporophyte,  and  while  this 
is  in  progress  the  endosperm-nucleus,  by  successive 
divisions,  develops  into  endosperm  which  surrounds 
the  embryo,  and  will  serve  to  nourish  it  when  it 
re-awakens,  at  the  "germination"  of  the  seed. 

L.  Fruit  and  Seed: 

1.  Meanwhile,  as  a  result  of  fertilization,  the  ovary 
resumes  growth,  and  develops  into  a  fruit  (ripened 
ovary),  while  the  ovule  enlarges  and  undergoes 
numerous  changes,  ripening  into  a  seed. 

2.  In  a  concisely  worded  paragraph,  tell  what  a  seed 
is,  stating  to  which  of  the  alternating  generations 
the  seed-coats,  endosperm,  and  embryo  belong. 

M .  Nutrition: 

i.  Discuss  the  nutrition  of  both  the  gametophyte 
and  sporophyte  of  Trillium,  as  suggested  above 
(L,  1-4,  p.  1 60)  for  Zamia. 
N.  Tabular  Review: 

Fill  in  the  tables  below  (pp.  190  and  191),  by  placing 
an  x  in  the  proper  space,  then  state,  in  a  well- 
worded  paragraph  for  each  table,  what  may  be 
learned  by  an  inspection  of  it. 


MORPHOLOGY  AND   LIFE   HISTORY 


TABLE  III. — COMPARISON  OF  GAMETOPHYTES 


Plant 

Respires 

1 
1 

| 

PH 

Has  stomata 

Takes  nourishment 
from  the  soil 

.a 

bo 
| 

1 

VI 

& 

! 

sit 

Partly  parasitic  on 
the  sporophyte 

Wholly  parasitic  ori 
the  sporophyte 

Monoecious 

Dioecious 

Capable  of  asexual 
propagation 

Has  both  vegetative 
and  rep  reductive 
functions 

Vegetative  functions 
^reduced 

Riccia      

I. 

2 

3 

4 

5 

6 

7 

8 

9 

10 

II 

12 

13 

Anthoceros 

Sphagnum 

\ 

Polypodium        .   . 

Equisetum 

Lycopodium 

Selaginella 

Isoetes 

Zamia 

Pinus 

Trillium          

MORPHOLOGY  AND  LIFE  HISTORY 


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- 


DEC       W3 


DEC  l  i;  8 

TTB1T5W 


MAY  -  8  1972 


MAY  -  6  197?  1  7 


LD  21-50m-6,'59 
(A2845slO)476 


General  Library 

University  of  California 

Berkeley 


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